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NOSES iia PSYCHOLOGICAL REVIEW PUBLICATIONS hed ne 16l 


Psychological Monographs 


EDITED BY 


SHEPHERD I. FRANZ, Univ. or Catir., So. Br. 
HOWARD C. WARREN, Princeton University (Review) 
JOHN B. WATSON, New York (J. of Exp. Psych.) 
MADISON BENTLEY, University or Itiinots (Index), and 
S. W. FERNBERGER, University oF PENNSYLVANIA (Bulletin) 


Further Studies in Retroactive 
Inhibition 


Sa, y 7 


ERNEST BURTON SKAGGS, Pu.D. 
College of City of Detroit 


PUBLISHED FOR 
Tue AMERICAN PsyCHOLOGICAL ASSOCIATION 


By THE PSYCHOLOGICAL REVIEW COMPANY 
PRINGELON GN, J: 
AaAnp ALBANY, N. Y. 


Acents: G. E. STECHERT & CO., Lonpon (2 Star Yard, Carey St., W. C.) 
Lei1pzic (Hospital St., 10); Paris (76, rue de Rennes) 





PREFATORY NOTE 


The experimental investigations reported in this paper were 
begun in the fall of 1920, although interest in the problem and 
some preliminary probing (largely by group methods) goes back 
several years previous to that date. This section of the work was 
completed in the summer of 1922, being carried on continuously 
during the interval. During the progress of these experiments 
several monographs and articles appeared dealing with certain 
phases of the work reported in this paper. However, it seemed 
worth while to continue the work as planned, believing that addi- 
tional experimental data would either help confirm or refute 
present theories and experimental conclusions. 

In view of the fact that several recent investigators have given 
very complete reviews of the past theoretical and experimental 
work done under the caption of retroactive inhibition (see bibliog- 
raphy at the end of the paper, numbers 1, 4, and 5), we will omit 
this customary procedure. However, we may note that many 
specific problems’ yet remain to be investigated under the heading 
of retroaction. For adequate treatment of these various prob- 
lems far more work remains to be done than has yet been 
reported. 

We wish to expressly state our obligations to Professor F. C. 
Dockeray, head of the department of psychology at Ohio Wes- 
leyan, who not only served faithfully as a subject for two years 
but did all in his power to see that adequate apparatus was pro- 
vided for the work. -Also we wish to thank the administrative 
officers of Ohio Wesleyan whose kind and generous regard for 
research made the present work possible. To Professor Pills- 
bury, under whose direction the work was done, we wish to 
express our appreciation for his various suggestions and encour- 
agement in the work. Last of all, we must express our appre- 
ciation to Mrs. E. B. Skaggs, who not only served throughout as 
a trained subject but also acted as experimenter when the writer 


worked as subject. 
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Digitized by the Internet Archive 
in 2022 with funding from 
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https //archive.org/details/furtherstudiesin00skag _ 


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TABLE ORS CONTENTS 
PART PAGE 
PRE RA TORVENOTE) foe oc thats re eke ee tt eee ee ea ea ce ili 


I. INTRODUCTORY STATEMENTS, DEFINITIONS AND As- 


SPPAA ELTON See sis 12’ Cavan sh Arcane eae aR Rue ge he 1 

eMC GUN STRUCTION “LEST. Mie ee men etme oo uare ice > 
A. Comparison of Work and Rest Intervals......... 5 

B. Retroactive Effects under Conditions of Fatigue... 14 

Crh feciiof Practice on Ketrodcttony.. Ma. ak eo os 18 

D. Effect of Varying the Temporal Interpolation.... 20 


E. Degree of Similarity Between Learning and Work 25 
F. Qualitative; Nature of the Rest and Work 


EULENVIOUSE Oot eae eee ae Ra ets, eae ee a2 
TU etna EN Sia VY RUSS 2 ocr acl eed Mayas MM Belle Raat ere ni eve leds 35 
A. Comparison of Work and Rest Intervals......... 35 
dead ON etal ig ay NEG ght at Yor Aponie n OP Da ene Cs Sah At A 39 
C. Postiton of Expervment in Day's Sertes......... 5) 
D. Effect of Temporal Interpolation............... 40 
PREELON GENS OV LT ABLES 0d yaa, bale daig, Mio) « 4 als sbepukdiats 42 
A. Comparison of Work and Rest Intervals, Single 
NETS A a Cope ee eek ehipert cs Co at + Sa LER a 42 
B. Paired Associates, Rest and Work Intervals; Sim- 
arity of Work and Learning. «.....6....6.6) 45 


C. Single Syllables, Similar versus Dissimilar Work.. 49 
D. Effect of Varying the Temporal Position of Work, 


POEIEG IA aS VILODLES 9 a le aanate Cine abd ido Sees 50 

E. Effect of Varying the Temporal Position of Work, 
BaredaAssociates: Method ncisiaee Ca neta ey 52 
V. GENERAL SUMMARY OF INVESTIGATION............ 56 
Te BUIOCE ABE Vernal, is Goby inl, Aa ome ine anna Caan, 59 


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4 





PART I. EXPERIMENTAL SECTION 


INTRODUCTORY STATEMENTS, DEFINITIONS AND ASSUMPTIONS 


Meaning of the term “retroactive inibition.” In this paper 
the terms retroactive inhibition, retroactive interference or block- 
ing, and retroaction will be used interchangeably. If any given 
mental (neural) activity B, following a previous learning process 
A, works detrimentally upon the retention and recall of learning 
A, we denote the fact by saying that there has been retroactive 
inhibition. We are using the term, not as any theory, but merely 
as a handy grouping for a number of phenomena. In psychi- 
atrical work cases are reported under the heading of retrograde 
amnesia. Here some physical shock or emotional disturbance 
seems to blot out the possibility of recall of events just preceding 
the shock. While these cases may involve very different prin- 
ciples of explanation from those facts reported in this paper, we 
are inclined to classify them under the heading of retroactive 
inhibition. On the more normal side, if one forms a given series 
of associations and then turns to other vigorous mental work 
(with or without emotional aspects), and finds that the original 
learning is recalled in an unsatisfactory way or not at all, then 
we indicate this fact as due to retroactive interference. 

Subjects used in the experiments. We may classify our sub- 
jects into three groups. One group may be called the “ trained 
group.” F. C. Dockeray, Mrs. E. B. Skaggs, and the writer 
constitute this group. All were trained in the art of giving keen 
and thorough introspections and were able to adjust themselves 
to the conditions of the experiment. 

The second group may be called the “semi-trained group.” 
They were students who were taking advanced courses in psy- 
chology following a year of general psychology, involving labo- 
ratory work. One of these was a graduate student (R. M. B.). 
Ali were faithful in trying to live up to the conditions of the 


‘ 


2 ERNEST BURTON SKAGGS 


experiments. Their introspections were usually inferior to those 
of the trained group. 

The third group consists in untrained subjects taken from the 
writer’s classes. The number of records from each of these 
subjects was usually small, and hence we must rely upon the 
central tendency of each group for indication of the actual facts. 
In all cases these subjects were used as checks, although their 
results were often quite convincing. 

The work and rest intervals. As we must in some way com- 
pare results under conditions where mental activity follows the 
original learning with those results where a period of rest fol- 
lowed the learning, it is very necessary to control these two mental 
conditions. In one case we want an extreme of mental struggle 
and attention. In the other case we want the subject to be just 
as passive mentally as possible—to relapse into a condition of lazy, 
passive perception. We have used the term Work Interval to 
denote a period of vigorous mental activity. The term Rest | 
Interval denotes a period of relative mental quietude and relaxa- 
tion. We have made no attempt to secure a graded series of 
mental conditions ranging from one of these extremes to the 
other. Our best rest period never represents complete passivity 
(this presumably would be death), but merely a condition of 
relatively little thought and effort. 

We believe that, on the whole, our subjects have been fairly 
successful in taking these two mental attitudes, one of work and 
one of rest. Each subject was told as clearly as possible our 
conception of a good rest and a good work period. In the rest 
interval the subject was urged to relax and assume a lazy, indif- 
ferent attitude. He was told not to worry about the score he 
made and to get away from the learning material as far as pos- 
sible. If at any time some part of the original learning came to 
mind he was to take a discouraging attitude toward it and get it 
out of his mind as best he could. In the case of the work interval 
he was told to work as if his “ life depended upon it.” 

Introspections. The introspections are absolutely essential in 
the following experimental work. Without these introspections 
the experimenter is unable to classify the rest and work interval. 


FURTHER STUDIES IN RETROACTIVE INHIBITION 3 


Only a complete history of what went on in the subject’s mind 
can permit the experimenter to say that “this is a good rest 
period free from any return to consciousness of the original learn- 
ing material,’ or “this is a fair rest period in which fragments 
of the original learning came to mind,” etc. It is upon the intro- 
spections of the three trained subjects that we have relied for 
the most part. Our group two (semi-trained subjects), however, 
contributed valuable introspective reports. 

While the introspective reports have not been given in this 
paper they have been taken carefully and in detail. Several 
tables and important conclusions have been based entirely upon 
the introspective reports. 

The use of short intervals. Our experiments everywhere 
employ very short rest and work intervals. Longer intervals were 
used at first (e.g., fifteen minutes) but very quickly abandoned. 
Long intervals bored our subjects and made it very hard to con- 
trol the rest interval. Long intervals put a premium upon all 
sorts of mental activity. Again, it was almost impossible to get 
the detailed introspections which we desired after a long interval. 

Program of. investigation. All experiments were performed 
individually. The writer was experimenter in all cases excepting 
when he himself served as subject. In the latter case I. D. S. 
served as experimenter. The so-called “ reconstruction test ”’ 
was used as test material in Part II (following). In Part III 
a little work is reported in which unconnected sense words were 
used as learning material. Nonsense syllables constituted the 
learning material in Part III of this report. 

We have attempted to gain some further data upon several 
major problems. First, Is there any definite evidence of retro- 
active inhibition? Here we have compared results after work 
and rest intervals. Second, Does the temporal position of the 
interpolated work affect the degree of retroaction? Here we 
have varied the temporal position of the work interval while keep- 
ing other conditions as constant as possible. Third, Is there 
greater retroaction when the work material is similar or dissimilar 
to that of the original learning? Is there any relation between 


4 ERNEST BURTON SKAGGS 


the degree of this similarity and the amount of retroactive inhibi- 
tion? Fourth, Is retroaction greater in the morning or eve- 
ning—when the subject is relatively fresh or when fatigued? 
Fifth, What is the effect of practice in a given learning material 
upon its susceptibility to retroaction ? 


PART II. EXPERIMENTAL SECTION 
RECONSTRUCTION TEST AS LEARNING MATERIAL 


Experiment Series A. Comparison of Rest versus Work 
Intervals 


In this series of experiments our problem may be stated as 
follows: Is there any positive evidence of retroaction under the 
conditions of our experiment? These conditions are: using the 
reconstruction test for original learning; short exposure (learn- 
ing) of material; short interval of work or rest; addition as the 
interpolated work; and using the central tendency as index for 
comparative purposes. 

The reconstruction test was used extensively because (1) other 
workers had used it to some extent (DeCamp and Robinson) and 
(2) because we found that it lent itself admirably to the experi- 
mental needs. 

Apparatus and Method: A chess board 12x12 inches was 
framed and covered with glass. Five chess men were used, viz., 
the queen, castle, bishop, knight, and pawn. A large white card- 
board 20 x 24 inches was arranged to slide up and down on a 
horizontal rod above the table, being used to screen the chess 
board and experimenter from the subject when needed. A stop 
watch was used in the timing. 

The subject sat on one side of the table, the experimenter on 
the other. The screen being down, E. arranged the chess men 
on various spots, under a prearranged schedule. At a warning 
signal of “ready” E. lifted up the screen and exposed the chess 
formation. S. was then given fifteen seconds in which to study 
the arrangement. The card was then dropped. The experiment 
now took one of two forms, as the case might be. Either (1) S. 
relaxed and was at rest for a given interval or (2) S. worked 
attentively adding columns of two place numbers. Three differ- 
ing intervals have been used, namely, a half minute, a minute, and 


6 ERNEST BURTON SKAGGS 


a two-minute interval. At the end of the given interval, work or 
rest, the screen was raised and S. tried to reconstruct the forma- 
tion. The time was recorded from the time S. began to recon- 
struct until he signified that he had finished. S. added aloud 
and a record of his performance was kept. However, the amount — 
of work thus done in the work interval is nowhere given in this 
paper, as it was found to be a relatively constant factor. 

The errors are calculated in the same manner as that noted in 
DeCamp’s work. Thus, if the queen was located by E. as four 
rows up and six columns over to the right our original record read 
simply, 4-6. If S. replaces the queen as 5-7, then the total errors 
are one for the row displacement and one for the column displace- 
ment, or a total of two errors. 

On any given experiment day six individual experiments were 
done, three of work and three of rest. The intervals were alter- 
nated for the following subjects: F.C.D., I.D.S., E.B.S., M.S., 
F.Bl., and Deus. Consequently each subject in this group knew 
what experiment was coming next. In the case of subjects © 
R.M.B., R.S., W.A.D., and Sh., the experiments were presented 
in irregular order, and hence these subjects did not know what to 
expect next. An interval of from two to three minutes elapsed 
between each individual experiment in the day’s series. 

The following tables (I to V, inclusive) give the Means and 
M.V. for the ten trained subjects and for ten untrained subjects. 
(It is to be mentioned that only subjects I.D.S. and F.C.D., 
and E.B.S. knew definitely the nature of the problem.) For the 
most part the averages for the trained subjects are based upon 
twenty experiments for each work and rest interval. As we 
desired some data of a comparative nature between morning and 
evening conditions, three subjects have thus data for both these 
times. 


7 


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10 


ERNEST BURTON SKAGGS 
TABLE V 


SHOWING CoMPARATIVE ReEsuLTS AFTER WorK AND Rest PErtops For 10 


Sex 


Female >. v2). 
Remaleyeric ae. 
Mailer, see scaaiebom ates 
Malewectann 
Females sce 
Male... 


Female. . 
Female. . 


otal 
M 


UNTRAINED SUBJECTS. AVERAGES BASED oN 6 RECORDS FOR 


EACH METHOD PER SUBJECT. 1’ INTERVAL USED 


Work Interval Rest Interval 
Br ye Tine Oy Er. otime @) 
8.5 48.8 Zeal 24 
1152 41.2 10.0 36.2 
10.0 143.8 6.8 125 
4.5 88.7 5.0 87 
9.2 103.3 3.8 93.3 
F a By AMELIE ERS aide 12.0 5755 8.5 5132 
Femaleniy (00/5 seu anies siete erences tas Ons 44.0 6.5 67.0 
9.3 7a adh S/o 
Uh vehi tonts atten ike 10.8 27.0 3.8 24.7 
Malencnde rs) 38.8 or3 SSIs. 
90.7 663.0 58.5 578.8 
APE EWS seg wpa tei Gena ae ls 9.07 66.3 5.85 57.9 
see teat 1.61 28.7 Ze3r 28.2 


A study of the foregoing data indicate the following: (1) As 
regards errors made, the case is quite clear for all intervals used— 
in the case of trained subjects. The performance after the rest — 
is much better than after the work interval. 


(A) For the half-minute interval the mean error is more than 


(B) 


(C) 


twice as large after the work than after the rest interval 
(8.55 as compared with 4.21). 

For the minute interval we also find the average error 
clearly larger for the work interval (9.04 as compared 
with 5.95). 

For the two-minute interval we likewise find more errors 
after the work. 


(2) Considering the above data with regard to individual per- 
formance rather than group average, we find: 
(A) For the half-minute interval all subjects do markedly 


(B) 


better after the rest interval. 

For the minute interval, where we have ten cases, eight 
subjects do better after the rest interval. Deus., one of 
the exceptions, persistently reported an inability to take 
a restful, passive attitude, and we suspect that her so- 
called rest period was as strenuous as her work period. 
R.M.B., the other exception, reported a similar con- 


FURTHER STUDIES IN RETROACTIVE INHIBITION 11 


dition, with the added fact that the adding was very easy 
for him. ; 

(C) For the two-minute interval (nine subjects) we again 
find two apparent exceptions, namely, Deus. and W.A.D. 
We believe that we can easily explain the record of 
Deus. (as above stated). W.A.D. has a mean based 
only on eight records and moreover could hardly be 
called a trained subject. 


(3) As regards reconstruction times, our summary table II 
shows that the mean time is consistently longer for the work than 
for the rest periods. 

(4) The evening records for subjects F.C.D., I.D.S., and 
F.C.D. (Tables III and IV) show the same thing—there are 
markedly more errors after the work than after the rest interval. 

(5) Table V gives the results for ten untrained subjects. 
Here only the one-minute interval was used and the records are 
based upon only six experiments for each work and rest interval. 
Inspecting the group averages, we find (1) more errors are made 
after the work than after the rest intervals (9.07 as compared 
to 5.85) and (2) the reconstruction time is longer after the 
work. Looking at the data from the standpoint of individual 
performance, we find that eight out of the ten subjects do better 
after the rest interval. 


Supplementary Control Series 


(A) 


It may be objected that the reason our subjects did more poorly 
after the work series was due to the fact that they were fatigued. 
Or, again, it may be objected that directly after the work the 
subject was so far removed from a “ reconstruction attitude ”’ 
that he could not get back into this attitude easily and so gave up 
too quickly. Our work intervals were so short (two minutes 
being the longest) that the fatigue objection seems out of the 
question. As six experiments were done in succession, with a 
small interval between each, there would have to be a most 


12 ERNEST BURTON SKAGGS 


remarkable oscillation between fatigue and recovery for these 
short intervals—something quite foreign to what we know of 
nerve and muscle fatigue. Muller and Pilzecker and Heine have 
also demonstrated that the above objections are largely insignifi- 
cant. As regards the attitude objection, we have often found that 
the subject was “ farther away” from the experiment at the end 
of the rest than after work. 
However, a control series of experiments was done, largely to 
meet the above objections. The reconstruction test was used as 
before. The exposure time was fifteen seconds. The work con- ~ 
sisted in adding two columns of figures simultaneously. The 
total time elapsing between learning and reconstruction was three 
minutes. In one case the subject rested for three minutes. In 
the other case the subject worked immediately for one minute 
and then rested the last two minutes. This experiment should 
largely do away with the above objections. Four subjects did the 
experiments, the order of presentation being irregular in all cases. 
The averages are given in Table VI. 


TABLE VI 
Work Interval Rest Interval No. Records 
Subject Er. Time Er. Time Based Upon 
R.S. Wane 57.8 4.6 47.6 10 
HG) ee ea ee de ol sere 12.0 37.0 3:45*, 34.0 9 
Bee B Ox. car eee antares Byles capt Spilby byes 13 
IDsS = Daas eee eee ee sate, See 3.6 47.2 10 


As in the foregoing experiments, we find here a clear retro-. 
active effect for three subjects. E.B.S. alone shows no retro- 
action; in fact, the reverse is true. We can offer no explanation 
for this change excepting that through constant practice the 
subject learned the formations so well that no retroaction could 
operate. 

(B) 

There may be a further objection to our view that the work 
activity in some way actually is detrimental to the previous learn- 
ing. The introspections of our subjects indicated that many rest 
intervals were characterized by at least some consciousness of the 
original learning.. This consciousness would vary from a mere 


FURTHER STUDIES IN ‘RETROACTIVE INHIBITION 13 


vague and fleeting thought of the learning to a vivid picture 
repeated a number of times. It may be claimed that the advan- 
tage of the rest interval lay in this very fact, namely, that during 
the rest the subject repeated the learning whereas during the work 
he could not. The point is a very crucial one. We have care- 
fully gone through the records of subjects F.C.D., I.D.S., and 
E.B.S., selecting, upon the basis of their introspections, those rest 
records which were free from any consciousness of the original 


TABLE VII 


CoMPARING AVERAGES OF SELECTED Rest INTERVALS WITH WorK INTERVALS AND 
witH TotTaL UNSELECTED Rest INTERVALS. RECONSTRUCTION TEST. THREE 
TRAINED SuBJECTS. MorNING AND EvEeNING ReEcorps. ONty Errors 


CONSIDERED. 
Morning Records 
. 0.5’ Interval 1.0’ Interval 2.0’ Interval 
Subject Rest Work Rest Work Rest Work 
PSDs abd cigs ney iosoo 8.70 4300) (11:20 8.70 12.1 
N, 17 N, 8 N, 3 
(4.2) (3.0) (6.3) 
Pears Sc tet wie) “OLGU 7.90 7.85 9.25 8257 hastoso 
N, 17 N, 14 N, 14 
Oe35) (7.0) (8.70) 
BiG Dye Peek eee. 4520 8.30 2.00 8.30 ar 20 EeLOeo 
N, 5 N33 N,5 
(4.3) (4.5) (5.4) 
Evening Hour 
ed Sie Me adler Bea ph LOU 7.60 4.83 7.80 3.86 9.70 
N, 10 N, 6 N, 7 
(1.95) (4.30) (3.20) 
Te eltoen Ma Bess «fos ots 20 ap 4.83 7.30 5.44 12.45 
N, 10 N, 12 N, 9 
(5.40) (4.75) (7.20) 
PO AE, Ve Ses 9 | 7.95 3.50 6.50 3.00 10.60 
N, 4 N,8 N, 3 
(3d) (2.9) (3.6) 


Expianatory Notes.—N represents the number of records upon which the average of 
the selected rest interval is based, The average given under Work is understood as based 
upon 20 records. The number in parentheses gives the average for the total unselected rest 
intervals as given in the preceding tables I and III. 


learning, with the exception of a short after-image which was 
always present. These three subjects’ records have been chosen 
because they furnish the most reliable and detailed introspections. 
Table VII gives the results in summary form. The data show 
that not only are these selected records confirmatory of our above 
stated view of retroaction, but the averages for the selected rest 
intervals are BETTER than the average for the whole series from 


14 ERNEST BURTON SKAGGS 


which they are taken. We are not surprised at this, for we recall 
that the subject often said that the consciousness of the original 
material was vague, indefinite, and merely signified that he was 


not sure of the learning. While some of the return thoughts of. 
the original learning may have helped the subject in the rest. 


experiments, we believe that there is evidence that the rest period 
gains its advantage over and above this. | 

We believe that our data amply justify us in saying that atten- 
tive work, following the original learning of the reconstruction 
test, works in some positive way a clearly detrimental influence 
on the retention and recall of this original learning. 


Experiment Series B. Comparison of Retroactive Effects under 
Conditions of Fatigue 

Tolman (5) found evidence that retroaction is greater for 

evening than for morning conditions, suggesting that retroaction 


operates more clearly under conditions of fatigue. Following: 


are two studies which bear upon this problem: 


(1) Comparison of average error and retroaction in the initial 
and final experiments of a day's sitting. 


It will be recalled that at a given sitting six experiments were 


performed. We may assume that the subject was at least slightly 
fatigued at the end of the session. In the following tables (VIII 
and IX) we present the averages for the initial and final experi- 
ments for four trained subjects. Thus, e.g., our day’s experiments 
would be 1, 2, 3, 4, 5, 6—the odd numbers representing work, the 
even numbers rest, intervals. We thus compare 1 and 5 and 


TABLE VIII 


CoMPARING AVERAGE Errors AND RETROACTION IN First AND LAST 
EXPERIMENTS IN SERIES 


- Position 0.5’ Interval 1.0’ Interval 2.0’ Interval 
Subject inSeries W R W-R W R W-R W R W-R 
Evening Hour 
E.B:S. First 5.4 8.0 (-2.6) 8.0 5.0 (3.0) 12.0 86 (3.4) 

Last BS Zin edleihsiey 6.26.5) 0-13} 8.6 5.2 (3.4) 

1 WIN Seno First 6.5 2.0 (4.5) i AN ee TM) Senn 24° Cie 
Last 10.41) 2.65)47:3) 12.1 41 (8.1) 13.6. 5.27) {648 

F.C.D. First 8.0 6.0 (2.0) 8.0) 27a dd. Lb ae 
ast 10,5)" 8.5" (20) 13;2-"4,9" 4833) 17.5" 7.1" (i049) 


FURTHER STUDIES IN RETROACTIVE INHIBITION 15 


2 and 6 in order to answer whether more errors are made in the 
final experiments of a day’s series. To find out whether retro- 
action is greater or less in the first or last part of the day’s series, 
we have taken the difference between 1 and 2 and compared it 


TABLE IX 


CoMPARING AVERAGE ERRORS AND RETROACTION IN First AND LAST 
EXPERIMENTS IN SERIES 


Position 0.5’ Interval 1.0’ Interval 2.0’ Interval 
Subject inSeries W R W-R W R W-R W R W-R 
Morning Hour 
E.B.S. First 74 46 (28) 11.9 7.0 (4.9) 11.9 11.2 (-.3) 
Last 8.68074. 8 Clk) 85 64 (2.1) 114 74 (4.0) 
EDS: First G16 14 a2) CLUE OLA MAL GO) TO:2p ois Coro) 
Last 13.0546:5)5.:(615) 133071267 (4.0) 13.4 64 (7.0) 
EG. D: First Ba 2 Coe) SRS eA GERD Bi7ou Ss ato) 
Last OS Ses CA) 10.1 6.0 (4.1) 17.1 6.7 (10.4) 
M.S. First 8.0 5.6 (2.4) 85:9 2:5)) 44 45 (-.1) 
Last 93 14 (7.9) 13.0 64 (6.6) ile tem G0)) 


with the difference between 5 and 6. The figures in parentheses 
give the retroaction; the other figures give the average error 
made. 

An examination of the preceding tables shows that the average 
error for both work and rest intervals is larger for the final 
experiments in a day’s sitting as compared with the average error 
for the initial experiments. Thus we find that out of twenty-one 
possible comparisons in our tables fifteen give a larger error for 
the final series, in case of the work intervals. Likewise, in case 
of the rest intervals, seventeen out of the possible twenty-one com- 
parisons indicate greater error for the final experiments. This 
may be due to fatigue or some intra-system inhibitory conditions 
which operate more as the experiments proceed. Both of these 
factors may work together. 

As regards the relative amount of retroaction, we find, compar- 
ing the figures in parentheses, that the greater retroaction occurs 
in the final experiments of the day’s series. Out of the twenty- 
one possible comparisons, fourteen give greater retroaction for 
the final experiments. In two comparisons there is apparently 
no difference. 

The facts seem fairly clear, indicating that in a learning process 
extending over about an hour’s duration there is more retroaction 


16 ERNEST BURTON SKAGGS 


for the material learned near the end than for that learned near 
the beginning of the process. Doubtless we are dealing with a 
condition of accumulated fatigue plus a slackening of interest or 
incentives to do one’s best in the final experiments of the day’s 
sitting. Also there must be added a possible accumulative system 
of interferences due to the previous learning: Our subjects con- 
stantly reported that they could think of previous constructions 
and that it troubled them. However, until we disentangle the 
respective influences of the two above mentioned general factors, 
we do not feel safe in declaring that our findings support Tol- 
man’s conclusions. The presumption would seem to be that 
retroaction finds a fertile soil upon which to work in the case of 
fatigue condition or where the learning itself is poor. 


(2) Comparison of retroaction under morning and evening 
conditions. 


The second part of our present contribution to the question 
of the relation between retroaction and fatigue is based upon a 
comparison of retroaction under morning and evening conditions. 
Subjects F.C.D., I.D.S., and E.B.S. did evening experiments 
(7 to 9 p.m.) in addition to morning experiments (7 to 9 a.M.). 
The morning and evening experiments were carried out in alter- 
nating fashion, thus ruling out practice effects. No subject did 
morning and evening experiments on the same day. Our assump- 
tion is that the subject is more fatigued in the evening than in the 
morning—that morning represents a condition of relative freedom 
from fatigue. 

In order to decide whether there is greater retroaction present 
in the evening experiments certain conditions must be fulfilled: 
(1) The average error difference between the work and rest 
series in the morning must be LESS than the average error 
difference between the work and rest series in the evening; (2) 
the learning in the evening for the rest series and work series 
must be as good as that in the morning, otherwise the difference 
between morning and evening results may be due to difference in 
degree of learning in the morning and evening. 

Using a series of conventional symbols we may put the matter 


FURTHER STUDIES IN RETROACTIVE INHIBITION 17 


thus: Let Er.W stand for the average error in the morning work 
series; let Er.R represent the average error in the morning rest 
series; let Er.w stand for the average error in the evening work 
series; and finally let Er.r signify the average error for the even- 
ing rest series. Then if there is greater retroaction in the 
evening, we have 


Er.W—Er.R < Er.w—Er.r, 
Granting, Er.r is not > Er.R 


The last condition is satisfied in our experiments. Much to 
the surprise of subjects E.B.S. and I.D.S., the evening learning 
was just as good as that of morning after the rest interval. 
F.C.D., however, demanded more exposure time to fulfil this 
condition and was accordingly given twenty seconds’ exposure 
instead of fifteen, as in the case of the other two subjects. 


TABLE X 
Subject: F.C.D. 
4’ Interval: W-R= 8.3 -4.3 =4.0 Slightly greater R. in Evening 
w-r = 7.95-3.7 =4.25 (Diff.=0.25) 
1’ Interval: W-R=10.1 4.55 =5.6 Greater R. in Morning 
w-r = 65 -2.9 =3.6 (Diff. = 2.0) 
Zaeiuterval iW —kR = 13.5) 946.1 Greater R. in Morning 
w-r 10.6 -3.6 =7.0 (Diff. = 1.1) 
Subject: E.B.S. 
4! Interval: W-R= 7.9 -5.53=2.37 Greater R. in Morning 
w-r = 5.25-5.40—=-15 (Diff.=2.52—No R. in Evening) 
1’ Interval: W-R= 9.25-7.0 =2.25 Greater R. in Evening 
wer = 7.3 -4.75=2.55 (Diff.=0.30) 
2’ Interval: W-R= 15.5 -8.7 =6.8 Greater R. in Morning 
w-r = 12.45-7.2 =5.25 (Diff.=1.55) 


Subject: I.D.S. 


YZ’ Interval: W-R= 8.7 -4.2 =—4.5 Greater R. in Evening 
w-r = 7.6 -1.95=5.65 (Diff.=1.15) 


I’ Interval; W-R=11.2 -5.7 =5.5 Greater R. in Morning 
w-r = 78 -4.3 =3.5 (Diff. = 2.0) 

2’ Interval: W-R=12.1 -6.3 =5.8 Greater R. in Evening 
w-r = 9.7 -3.2 =6.5 (Diff. =0.7) 


The data obtained indicate that for these three trained subjects 
there is little or nothing to make us believe that retroaction is 
greater in the evening. Subject F.C.D. shows slightly greater 
retroaction in the evening when using the half-minute interval, 
but for the one- and two-minute intervals there is greater retro- 


18 ERNEST BURTON SKAGGS 


action in the morning. E.B.S. gets slightly more retroaction in 
the evening for the minute interval but greater retroaction in the 
morning for the other two intervals. I.D.S. alone gives evidence 
of greater retroaction in the evening, although in her case there 
is greater retroaction in the morning for the one-minute interval. 

Our subjects are too few in numbers to permit generalization, 
although for each individual we have tried to make the data con- 
clusive by securing a large number of records. As far as our 
evidence goes it is contrary to Tolman’s notion of greater retro- 
action in the evening. Moreover, our results make us suspicious 
that the facts indicated in section (1), preceding, are due to 
accumulative interference systems rather than to mere fatigue 
accumulation. 

The results of the section above and the preceding section seem 
in conflict. However, it must be remembered that in section (1) 
the subject was probably losing his incentives to learn, while in 
section (2), when working in the evening, the subject was thrown 
into a condition whereby he put forth extra effort to overcome his 
general fatigue condition. These differences in incentives and 
effort are, we believe, very complicating factors, and may explain 
the above mentioned differences. | 


Experiment Series C. Effect of Practice on Retroaction 


As one becomes more and more practiced with the learning 
material and the methods of learning that material, does retro- 
action tend to disappear? Robinson (4) found no retroaction in 
the case of one of his subjects who was very familiar with the 
chess board and chess men (reconstruction test): This suggested 
that the fact might be due to practice. 

We present the results for five trained subjects who have 
twenty experiments to their credit for each work and rest con- 
dition for each total interval used. We have taken the averages 
for the first half of the entire series and compared them with the 
averages for the last half of the series. The figures in paren- 
theses give the amount of retroaction. By comparing these 
figures for the first and last half of the total series we should gain 


FURTHER STUDIES IN. RETROACTIVE INHIBITION 19 


some light upon the question of the relationship between practice 
and retroaction. The amount of retroaction should be less in the 
second half of the experiments in case practice decreases retro- 
action. It should be noted that subject F.C.D. has played chess 
and that E.B.S. and I.D.S. have played checkers a great deal. 
Consequently all knew the chess board well before beginning the 
experiments. 


TABLE XI 
COMPARING AVERAGES AND RETROACTION IN First AND SEconD HALF oF 
EXPERIMENTS 
Subject: F.C.D. 
0.5’ 1.0’ 2.0’ 0.5/ 1.0’ 2.0’ 
Morning Evening 
Av. 1stl0(W) 8.9 13.9 15.9 13.0 133 
Av. 1ist10(R) 4.4 (4.5) 3.9 (10) “i i (4) DG tas Pee Ae 2a 3.3) 
Av. 2nd10(W) 7.6 6.4 17.8 S45) 2.6 14.0 
Av.2nd10(R) 4.2 (3.4) 5.1 (1.3) 5.7(12.1) 4.4 (1.1) 3.0 (-.4) 5.0 (9.0) 
TABLE XII 
COMPARING AVERAGES AND RETROACTION IN First AND SECOND HALF OF 
EXPERIMENTS 
Subject: M.S. 
0.5/ 1.0’ 2.0’ 
Morning 
Av.1st10(W) 8.9 11.3 8.9 


Av. Ist 10(R) ee aig Bape 
Av. 2nd 10(W) 9.7 SAS 9.9 
Ay.2nd10(R) 3.5 (6.2) 8.9 (0.2) 9.5 (0.4) 


TABLE XIII 
CoMPARING AVERAGES AND RETROACTION IN First AND SECOND HALF OF 
EXPERIMENTS 
Subject: F.BI. 
1.0’ 207 
Morning 

Av. 1st 10(W) 8.3 7.3 

Av. Ist 10(R) oF (7.0) a4 (5.6) 

Av. 2nd 10(W) 

Av. 2nd 10(R) 2 (68) 54 (05) 
TABLE XIV 


COMPARISON OF First AND SECOND HALF OF EXPERIMENTS 
Subject: I.D.S. 
0.5’ 1.0/ 2.0/ 0.5’ 1.0’ 2.0% 
Morning Evening 

Av. 1st10(W) 10.3 9.9 127 his 5.0 

Av. Ist 10(R) 2.9 (7.4) Fini eat8-2) 2.8 (4.7) ene 53.39) 
Av. 2nd 10(W) 7.1 8.0 

Av. 2nd10(R)_ 5.4 (1.7) EB (66) 60 (5A) 1.1 (6.9) 42 (64) MM (9) 


20 ERNEST BURTON SKAGGS 


TABLE XV 
COMPARISON OF First AND SECOND HALF or EXPERIMENTS 
Subject: E.B.S. 
0.5/ 1.0’ 2.0’ 0.5’ 1.0’ 2.0’ 
Morning Evening 


13.4 og. 6. 8.1 14.3 
1.7) 8.6 (4.8) eres 6) 7.9 (-1) eG; 2) 9AtSia) 
oe 53 6.5 10.6 
3.4) 5.4 (-3) 71 (43) Z9.(07) 1.2.45, 3) use oslo) 


Av.1st10(W) 85 
Av.1st10(R) 68 
Av. 2nd 10(W) 7.3 

Av.2nd10(R) 3.9 


( 
( 

If we take the total number of possible comparisons in Tables 
XI to XV, inclusive, we find twenty-three. Out of these twenty- 
three possible comparisons we find that eleven cases signify greater 
retroaction for the first half of the experimental series. Ten 
cases give more retroaction in the last half of the experiment 
series. Two cases are so close together that we may regard them 
as neutral. Looking at the comparisons by individuals, we note 
the following: Subject F.C.D. seems to reveal less retroaction 
as the experiments proceed, although in two comparisons the 
reverse is true. M.S. and F.BI. seem to indicate that retroaction 
decreases with practice. 1I.D.S. and E.B.S., however, indicate 
that retroaction increases as the subject goes on with the experi- 
ments. In the case of the former there are four comparisons 
giving greater retroaction in the last half as compared to two 
cases where the reverse is true. E.B.S. shows the same result. 

These results hardly justify us in making any definite statement 
as to the matter of the relationship between degree of retroaction 
and practice. The records of F.C.D., I.D.S., and E.B.S. are by 
far more significant than those of the other two subjects because 
they were thoroughly trained and have each six comparisons for 
inspection. Taking these three subjects, we find two experienc- 
ing greater retroaction in the last half of the work, while one 
does the opposite. 


Experiment Series D. Effect of Varying the Temporal 
Interpolation 
Muller and Pilzecker (3) and likewise Heine (2) found evi- 
dence that the sooner the interpolated work is introduced after 
the original learning the greater the inhibitory effects. Robin- 


FURTHER STUDIES IN RETROACTIVE INHIBITION 21 


son,(4) however, comes to the opposite conclusion. The whole 
Perseveration Theory is largely at stake here, and the settlement 
of this point is vital to any theory of retroaction. In view of 
the conflicting results thus far reported it has seemed well to test 
further this point. 

Again the reconstruction test has been used as original learning 
material. The total length of the interval between learning and 
attempted reconstruction has been kept constant. The only vary- 
ing factor was the temporal position of the interpolated work. 

The experiments fall into two different series as follows 
(figures represent minutes in all cases) : 


Series I. Total interval 10 mintes: 
Method I. Learn—Work 3—Rest 7—Reconstruct. 
Method II. Learn—Rest 3—Work 3—Rest 4—Reconstruct. 
Method III. Learn—Rest 5—Work 3—Rest 2—Reconstruct. 
Method IV. Learn—Rest 7—Work 3—Reconstruct. 


Series II. Total interval 5 minutes: 
Method J. Learn—Work 2—Rest 3—Reconstruct. 
Method II. Learn—Rest 1—Work 2—Rest 2—Reconstruct. 
Method III. Learn—Rest 2—Work 2—Rest 1—Reconstruct. 
Method IV. Learn—Rest 3—Work 2—Reconstruct. 


Series II was done after series I because the first results were 
rather unsatisfactory so far as indicating anything definite was 
concerned. In the first series we used multiplication of two by 
four place numbers as the work. This work was unsatisfactory 
because it became automatic too readily and appealed very little 
to the interest of the subjects. Consequently in series II, in 
addition to reducing the total time to five minutes, algebra prob- 
lems took the place of the multiplication. These problems were 
simple equation problems with which the subject could make 
headway in the short work time. 

On any day’s sitting the subject was given all the various 
methods, there being a rest of from two to four minutes between 
each experiment. To equalize the fatigue factors the methods 
were rotated from day to day. In series I, E.B.S. alone did all 
four methods listed above; the others did three. 


ee ERNEST BURTON SKAGGS 


Nine trained and ten untrained subjects participated in this 
experiment. Tables XVI and XVII give the individual averages 
for the trained subjects for both series I and II. Table XVIII 
gives the averages for the untrained subjects. Graphs I and II 
will give the same facts for the trained subjects as found in their 


tables. 
SUMMARY TABLE XVI 


SHow1NG AVERAGES FOR FIVE TRAINED SUBJECTS. EFFECT OF VARYING REST 
INTERVAL BETWEEN L AND W, REcoNstRUCTION TEsT; SERIES I 





W3R7 R3W3R4 R7W3 R5W3R2 
Subject Er, EB; Er. Ake ihn Ae Er ple 
Deus. 12.60 99.6 7.10 91.0 7.9 11.40 : Pe 
F.:G.D 8.47 58.5 8.00 51.9. 6.1 62.7 Be Ais 
I.D.S. 11.20 72.5 5.95 63.3 10.0 75.0 ier Ri ae 
M.S. 10.90 122.5 10.60 121.6 11.8 116.6 Bay, Weds 
FBS? 12.40 89.9 9.70 82.5 9.3 74.3 5.4 21.5 
Total 55.57 443.0 41.35 410.2 45.1 442.6 5.4 ZL5 
Mean 11.11 88.6 8.27 82.0 9.0 88.5 


SUMMARY TABLE XVII 


SHOWING AVERAGES FoR Four TRAINED SuBJECTS. EFFECT OF VARYING REST 
INTERVAL BETWEEN L AND W, REcoNstRucTION TEsT, SERIES II 





W2R3 R1W2R2 R2W2R1 R3W2 

Subject Er. ax Er. De Er. le Er. ‘ie 
F.BI. 3.13 2te 1.73 24.7 3.60 24.9 2.53 29.7 
E.B.S. 12.00 734 7.30 61.6 8.87 66.6 6.00. 76.0 
LDS: 9.87 62.0 8.00 56.7 7.47 52.8 8.87 58.7 
R.S. 10.91 74.4 10.50 71.4 8.83 86.9 9.00 75.0 

Total 35.91 230.7 27.53 214.4 287/23 kee 26.40 239.4 

Mean 8.98 eer | 6.88 53.6 7.19 57.8 6.60 59.9 


TABLE XVIII 
SHOWING AVERAGE TIME AND Errors FoR UNTRAINED SUBJECTS. EFFECT OF 
VARYING Rest INTERVAL BETWEEN L AND W. BASED UPON 
Four Recorps Eacu. Series II 





W2 R3 Rl W2 R2 R3 W2 
Sex Er, Ae Er, as Er, AY 
Female..... 5.50 68.5 5.00 56.3 5.80 120.5 
Female. . 1.50 44.0 4.75 36.3 ao 24.0 
Females. ac 6.75 45.8 B25 42.5 2.00 47.8 
Female..... 5.75 22.3 4.50 50.8 13.50 48.3 
Female... 8.75 81.7 12.50 90.0 Pio 125.0 
Female... 11.50 35.8 6.00 51.0 7S 42.5 
Female..... 15.25 61.5 8.25 35.3 eye 507 
Male visi tenucn 13.00 23.0 7.75 26.5 9.0 21.0 
Males ch Ae t 2.00 49.0 2.00 52.0 2.0 65.0 
Female... 3.20 41.6 1.60 25.8 4.6 64.0 
Motal eer 73.2 473.2 57.60 466.5 71.15 608.8 
Mean jy. cn uve s 7.32 47.3 5.76 46.7 732 60.9 
MEY ETRE erty 3.84 14.3 2.29 13.5 3.83 26.2 


FURTHER STUDIES IN RETROACTIVE INHIBITION 23 


Turning first to the averages presented in the foregoing table 
for series I, we note that most errors are made when the work is 
introduced immediately after the original learning. However, 
comparing methods II and IV, we find that the former gives the 
less number of errors. We cannot account for this unless the 
work, coming at the end of the interval and thus just before the 
reconstruction, leaves the subject in an attitude which is unfavor- 


GRAPH I 


FROM TABLE XXXTV 


FRRORS 





WS5R7 RBW3 R4 R7 WS 


| Sih" ay aaipitdanmyangs Attssspmaaad pera 


bef oe 8S =aeEEw eee aew eges Ge Soe 
PE) Soi Vash aleiee raceme aie al elnie sie a 
Deemed a air ety so omoen 1p ores coe 


PED cl een eens gees ces 


GROUP AVE 





24 ERNEST BURTON SKAGGS 


able to recall. Heine (2) found that this difference in attitude 
was insignificant in the case of nonsense syllables. Also, we 
have found very often that the subject was “ farther away ” after 
a rest than after a work interval, and our experiment testing the 
above assumption gave no evidence in its favor. 

Considering individual performances, which is more important 


GRY Str lt 


FROM TABLE XXxXW 


ERRORS 





W2 RS RIW2 R2 R2w2 Rl RSWS 


Faye ee 


GROVP AVE. 


FURTHER STUDIES IN RETROACTIVE INHIBITION 25 


here perhaps, we find that F.C.D. gives a nicely graded series 
(see Graph 1). His results fit the perseveration view nicely. 
E.B.S. has a similar curve, although the differences are not so 
marked between the various methods. The other subjects all 
show more errors when the work is introduced immediately but, 
peculiarly enough, get their best results by the intermediate 
method. 

If we now inspect series I] (see Summary Table XVII and 
Graph II, above), we find, comparing the extreme methods, 
W2 R3 and R3 W2, that the group average shows more errors 
when the work is introduced immediately. However, we again 
fail to secure a graded series, reading from left to right in our 
summary table or graph, as we might expect if the perseveration 
view is correct and our methods adequate. A study of the indi- 
vidual records shows clearly that the temporal position of the 
interpolated work is significant—the “ work-at-once ”’ method is 
the poorest. 

A study of Table XVIII, giving the results for the untrained 
subjects, indicates likewise that the temporal position of the work 
is important. The most errors are made when the work is intro- 
duced immediately after the original learning. 


’ 


Experiment Series E. The Degree of Similarity Between Inter- 
polated Work and Original Learning 


What is the relation between the degree of similarity of work 
interpolation and original learning as regards the amount of 
retroaction? Robinson (4) found evidence that retroaction is a 
function of the similarity between interpolated work and learning. 
Certainly the problem is a vital one from the standpoint of a 
theory of retroaction. If the work and original learning are 
identical, then we have mere repetition, and consequently mere 
reinforcement of the impression value and the associative bonds. 
But as the work becomes more and more dissimilar in content 
and method, where do we find a place where reinforcement stops 
and interference begins? Obviously two difficulties of experi- 
mentation appear. We must work out a priori a graded series 


26 ERNEST BURTON SKAGGS 


of work activities ranging from identical to dissimilar. Also 
we must see to it that these various work activities are equally 
taxing, equally interesting and absorbing. Both desiderata are 
difficult to attain. 

In the following experiment series we have tried to obtain 
further facts upon this problem of degree of similarity. Two 
series of experiments were carried on (I and II below). As 
these two series differed considerably we will take them up 
separately : 

SERIES | 


The reconstruction test was used as in previous experiments. 


The variable factor was the content of the interpolated work. 
The following outline will give the plan of procedure: 


(a) S. studies the chess men arrangement for fifteen seconds. 
This we designate simply the original learning. 

(b) S. rests one minute. E. arranges the work series. 

(c) S. studies the interpolated work for fifteen seconds. 

The content of this work was the varying factor. 

(d) S. rests for one minute. 

(e) S. is tested for thirty seconds on the interpolated work or 
else continues the work if it is multiplication. In case of 
reconstruction type of work, S. tries to reconstruct. In case 
of picture study, S. tries to recall all details. If S. finished 
the reconstruction or the recall of the picture details before 
the thirty seconds were up (this seldom ever happened) he 
continued to think over what he had just done. 

(f) S, rests one minute. FE. records the score made on the work 
and makes ready for the reconstruction of the original 
learning. 

(g) S. tries to reconstruct the original chess formation. 


The work material consisted of four varieties for all subjects, 
excepting I.D.S. and E.B.S., as follows: 


I. Similar work. Here S. studied a new chess formation and 
after one minute tried to reconstruct it. 





FURTHER STUDIES IN RETROACTIVE INHIBITION 27 


II. Intermediate form of work. A plain white cardboard was 
inked in heavy black lines such as to make sixty-four squares. 
This card exactly covered the chess board and was placed 
upon it during the work. Five articles were arranged upon 
these squares, namely, a large white button, large black 
button, a red checker, a black checker, and a pawn. _ S. stud- 
ied this formation and later tried to reconstruct it. Our 
assumption is that this work has some similarity to the 
original learning and yet differs in certain respects. 

III. Multiplication of two by four place numbers. Some sub- 
jects added double columns of figures instead, as the multi- 
plication became automatic. 

IV. Study of post card pictures of scenery. Here S. was told 
to study the pictures with the purpose of later recalling all 
possible details. These last two forms of work we have 
thought of as dissimilar and so signified in the following 
tables. 


Three to four minutes intervened between each experiment. 
A day’s experimentation included all four (or three, as the case 
might be) kinds of work. For I.D.S. and E.B.S. six chess men 
were used in the work series involving reconstruction work, 
whereas only five men were used for the other subjects. The 
order of presentation was rotated from day to day. The subject 
only rarely knew what kind of work was coming next. 

The tables giving averages for this experiment series follow 
(Tables XIX and XX). Table XLIII is a summary table for 
nine untrained subjects. 

If we will now compare the average error (Table XIX) for 
either of the dissimilar series (multiplication, or addition, on one 
hand, or picture study on the other hand) as over against the 
average error for the similar series, we note that the group 
means indicate that there is more retroaction where the work is 
similar. The reconstruction times show nothing. If we take 
the individual cases, as such, however, we find disagreement. If 
it is true that retroaction is a function of the degree of similarity, 
and if we really have three kinds of work differing in degree of 


28 ERNEST BURTON SKAGGS 


SUMMARY TABLE XIX 
DEGREE OF SIMILARITY, SERIES I, RECONSTRUCTION TEST. TRAINED SUBJECTS 
III. Dissimilar IV. Dissimilar 


I. Similar II. Intermediate (Adding) (Picture) 
Subject Er. Time Er. Time Er. Time Er. Time 
BC.D; 10.17 49.7 3.42 47.8 5:93) 37.3 6.63 44.9 
R.M.B. O70 62.4 11.90 66.4 9.80 91.9 15:38 65.4 
LDS! 15.42 80.9 19s P5983 6.07 tetas ad AAP ee bo eae) 
Epis: ISSA S38 125: 03.2 9.83 74.1 She PLP ee 
R.S 15.80 65.6 11°70). 64a! 1OES0 a7 bo 13,5097 02.4 


Total 65.26 312.1 46.19 300.8 48.73 322.1 $5.51) A724 
Mean 13.05 62.4 P24" O02 9.75 64.5 741 34.5 


ExpLanaTory Nore.—Averages given based upon 11 records for F.C.D., 10 for 
R.M.B., 12 for I.D.S., 12 for E.B.S., and 10 for R.S. The times of day when experiments 
were given eres 8:00 am., F.C.D.; 11:30 a.m. for R.M.B.; 7:00 p.m., I.D.S. and E.B.S.; 
7:00 P.M., 


TABLE XX 


RECONSTRUCTION TEST. DEGREE OF SIMILARITY, SERIES I. SHOWING AVERAGES 
FOR 9 UNTRAINED SUBJECTS, BASED UPON 5 Recorps EACH 





Similar Intermediate Dissimilar 
Sex Er. Time Er. Time Er. Time 
Bemaleseeu. ds cisthl ataedaur Onl 53.6 12.2 81.0 4.0 59.4 
Malem: cee een 80.2 9.8 42.8 Tome 36.2 
Hemales gd eo ce ae 57.6 9.8 34.8 7.4 39.0 
Female sinner el lce 61.6 6.2 56.4 9.8 56.2 
Pemalesta. 3 eeine: peels 48.8 6.0 32.8 Ae 34.2 
Bemalerse ao. ot vant a ae 0 93.5 £302 LOD ee 4.6 66.2 
Femaleaay vier ote ie aoe 0) 50.5 9.0 40.5 Tht 32.6 
Malele ec tene Mclean mene Ain Shoat TALE OL 6.5 2305 
Female...... (if 55.4 4.6 39. A’.6 ie S5kG6 
otal it Sat Pee ete ee LOR nS e7 78.35 464.9 62.1 382.9 
Meat a Smads tress del tlle 4ter 9c 6 8.7 Si Ong 42.5 
IME orc) RAE at iui Dies Ge Sine 2328 noid PRE OEORS 


similarity, then our summary table should show a decreasing 
average error as we read across from left to right. Method I, 
Similar, should give the greatest error; Method II, Intermediate, 
should give less errors; Method III, Dissimilar, should give least 
error. Unfortunately for such nicety of results, this is neither 
true for the group averages nor for individual means. F.C.D. 
shows least errors for the Intermediate method, although he makes 
most errors where the work is similar. I.D.S. and E.B.S. give 
results according to expectations stated above. R.M.B. gives a 
medley of results. He makes far more errors after studying the 
pictures than after any other kind of work; then in decreasing 
order of errors we find: Intermediate, Similar, and Dissimilar 
(adding). R.S. gives a similar irregularity of results. 


FURTHER STUDIES IN RETROACTIVE INHIBITION 29 


Table XX, the summary table for the untrained subjects, indi- 
cates that the similar work causes greater interference than the 
dissimilar. In fact, their table gives a nicely graded series of 
errors, aS we might expect. This is true for both time and errors. 

Our data seem fairly indicative of the importance of the degree 
of similarity and in so far confirm Robinson’s results. 


SrERIEs II 


Feeling that there was the possibility that the different kinds of 
work used in the previous series might have involved different 
degrees of effort and attention, an additional series of experiments 
were done. Also we were urged to carry out these additional 
experiments to test further the matter of finding the point where 
similarity ceases to be conducive to retroaction and turns into 
actual facilitation. Consequently in these experiments we have 
confined ourselves entirely to the reconstruction test both for the 
original learning and the work. According to the decreasing 
degree of similarity as we deduced it, three different work 
arrangements were used, indicated in the following tables as 
I, II, and III. ‘Work formation I was very similar to the original 
arrangement excepting that the chess men were removed in any 
direction by one square (in a few cases by two squares). Work 
arrangement II involved the using of the same squares as in the 
original learning (thus keeping the same pattern) but different 
men on these squares. We have considered this arrangement as 
intermediate. Work formation III consisted in as widely dif- 
ferent arrangement of the chess men with regard to the original 
formation as was possible. Thus if the original formation had 
the men clustered together, in the work they were widely scattered. 
This we have considered as the least similar work arrangement. 

The procedure was similar to that in Series I. Five trained 
subjects did the experiments. On a given experiment day all 
three experiments were done twice, with an interval of from three 
to four minutes between each. Table XXI gives the individual 
averages. 


30 ERNEST BURTON SKAGGS 


SUMMARY TABLE XXI 
DEGREE OF SIMILARITY, SERIES II, REcoNstRUCTION TEST. TRAINED SUBJECTS 


I vig III 

Subject Br: amen Er: Ww: Er, Time Er.W. Er. Time Er.W. 
BiG D2I GUE SF 6.7 140 118 10.6 518 14.0 
R.M.B. 95 90.9 6.4 18.6 58.9 rps) 11.0 45.1 106 
TDS: 5.8 74.6 oh 10.1 66.0 3.0 11:9)" 576 4.4 
E.B:S: 8.3 42.0 Sal 5.9 41.9 6.7 a Lede eaeL 5.9 
ieee 13.6 70.4 6.3 5.7 as.5 ed 124) <03.7 eee 

Total 40.4 273.0 26.6 47.0 239.6 34.1 58.5) 2915 east 


Mean 8.08 54.6 D2 94 479 682 117) 58.37 ee 


Norte.—Following are given the times of day and (in parentheses) the number of 
ips. vas veer sey Eel anne ¢ ee hig Coe (10) 5 GRAM. Bis 118A: M. (10); 

Taking the mean of the group of five subjects, we find 
that the just slightly dissimilar Series I gives the least mis- 
takes both for the reconstruction of the original learning (note 
column headed Er.) and for the reconstruction of the work series 
(see column headed Er.W.). Our so-called Intermediate Series 
II stands intermediate as regards both sets of error values. 
Series III, the most dissimilar series, gives MOST mistakes. It 
is of interest to note that there is an apparent relationship between 
mistakes in the original learning and the work series. A glance 
at the summary table shows that the smaller the error for the 
original learning, the smaller the error for the work, and vice 
versa. This may be indicative of interinhibitory or interference 
processes working backward and forward. Subjects F.C.D. and 
I.D.S. show a nicely increasing error value through Series I, II, 
and III. The increasing order of errors for R.M.B. is I, III, II; 
fOr HBS kle tills Oth ot LLALLe, Le 

From the standpoint of similarity of individual results our data 
are not satisfactory. The group mean, however, indicates that the 
most dissimilar work gives the greatest retroaction. Most of 
the subjects realized at once, in Work Series I, the fact that the 
change was slight. Here we approximated a mere repetition— 
at least definite relationship cues were present in the work arrange- 
ment which actually reinforced at times the original learning. 
Consequently we could hardly expect S. to make many mistakes. 
In Case II it was different. Although the same squares were 
covered as in the original learning, the chess men were rear- 





FURTHER STUDIES IN RETROACTIVE INHIBITION 31 


ranged on these squares. This tended to bring confusion. The 
subject realized at once that he was dealing with the same pattern 
but the complete changing about of the chess men in some way 
brought confusion. In Case III the work arrangement was as 
different from the original as possible and so appreciated by the 
subject. 

The introspective aspect of this experiment series has been 
especially elucidating and suggestive. On the basis of these 
introspections and the above tables we may venture the following 
conclusions and interpretations: 

(1) Least errors were made in Work Series I. This was 
because the similarity approximated identity too closely, permit- 
ting helpful relationships to be easily noted. This is another way 
of saying that we had enough identical elements (largely in the 
form of spacial contiguity) to afford a positive transfer effect, 
however small. 

(2) The Method II was intermediate in errors. This was so 
because it stood intermediate between helpful similarity (as noted 
in (1) above) and harmful degree of dissimilarity, as was found 
in Method III. It offered a greater degree of dissimilarity than 
Method II, there being less chance to note helpful similarities and 
differences. On the other hand, there must have been some few 
helpful relationships in this method because it was not so destruc- 
tive of retention and recall of the original learning as was 
Method III. 

(3) Method III gave most errors. Here the point of helpful 
relationship between work and learning (at least the point of 
relatively harmless relationship) is definitely passed and the work 
acts detrimentally. 

(4) If we make up a series of apparently varying degrees of 
SIMILAR work, all series of which use the same material and 
methods of learning as the original learning, then the MORE 
DISSIMILAR the material the greater the retroaction. 

(5) We feel that the above is in no way contradictory to the 
facts found by Robinson or the results found in our preceding 
Series I. As Robinson has suggested, if we begin with original 
learning and work interpolation as identical, then there will be, 


32 ERNEST BURTON SKAGGS 


of course, reinforcement, a mere repetition. As the work is 
made more and more different, there comes a time when the rein- 
forcing factors drop out or give way to interfering factors. Let 
us call this point, just mentioned, Point C. Up to Point C our 
statement above holds good. Here the greater the similarity 


the MORE the reinforcement and the LESS the interference. 


But as we go past this Point C the whole situation becomes 
reversed, and the more similar the material and method in the 
work the greater the retroaction, granting equality of attention 
and effort. This conception of the matter may be put in 
diagramatic form as shown in Diagram I. 


DIAGRAM I 


MAX} MUM 


AND INHIBITION 





AMOUNT oF REINFORCFMENT 


2 
= 
< 
k4 


SCALE OF DEGREE OF SIMILARITY - 


Ficure 3. Explanatory Note—The above diagram is merely theoretical in 
its outline. Possibly the curves may be drawn with some mathematical 
precision in the future. The scale on the left vertical represents the amount 
of reinforcement and retroaction—two opposed processes. The horizontal 
scale represents the degree of similarity between the original learning and the 


interpolated work. Beginning at A where learning and work are identical, as. 


we go to the right there is greater and greater dissimilarity until at D the’ two 
are as dissimilar in content and method as is possible. At A inhibition is at a 
minimum and reinforcement at a maximum (mere repetition); at C the 
situation is reversed. At D the inhibition curve has fallen but never to the 
original minimum. 


Experiment Series F. Qualitative: Nature of the Rest and 
W ork Intervals 


In Part I, Experiment Section preceding, we noted that the 
validity of our results rested largely upon the nature of the work 
and rest intervals. However, it is extremely difficult to secure 


. 
| 





FURTHER STUDIES IN RETROACTIVE INHIBITION 33 


many “ ideal” rest intervals—ideal in the sense that the subject 
was mentally passive and indifferent and entirely away from the 
original learning material. If one can secure ten such intervals 
out of twenty experiments, one is lucky. In a preceding section 
(see Table VII) we selected those experiments where the 
rest interval was characterized by practically no consciousness 
of the original learning after the after-image had faded away. 
No attention was paid as to whether or not the subject was 
“active ’’ mentally along other lines. A glance back at Table VII 
shows the proportion of “ ideal”’ rest intervals to the total of the 
rest intervals. In the case of the half-minute interval we note 
that there are 56 ideal rest intervals out of a total of 120; in the 
minute interval there are 51 ideal rest intervals out of 120; and 
in the two-minute interval there are 41 ideal rest intervals out of 
120. Obviously, as the rest interval is lengthened there is a 
smaller proportion of “ideal” rest intervals. We found that 
ten- and fifteen-minute intervals were not only conducive to all 
sorts of mental activity on the part of our subjects, but they 
tended to put a premium upon thinking about the original learn- 
ing. For this reason we have not used long intervals in this 
investigation. | 

It must be remembered that an “ideal” rest interval meant no 
return to consciousness of the original learning. If we would 
include those intervals where the subject reported merely a vague 
and indefinite and fleeting consciousness of the learning, our 
number of “ideal ’’ rests would then be much larger. The cases 
where a complete “return”’ of the whole learning came to mind 
were very few. The consciousness of the original learning thus 
ranged from a mere fleeting and fragmentary visual or sub- 
vocal representation to a review of the whole situation. In 
general, we may say that as the subject progressed with the 
experiments he was better able to take an indifferent attitude 
during the rest intervals. There was always a memory after- 
image which faded out in the course of one to three seconds. 

All subjects reported at times that they felt that the learning 
material was “near at hand” and ready to “break in.” F.C.D. 
was the subvocalizer of the group. Often the subject would 


’ 


34 ERNEST BURTON SKAGGS 


report that a mere visual image of one or more chess men would 
flash into mind and out again without being connected with any 
chess board. At times a part of the chess board or the whole of 
it would flash into mind without any men placed upon it. Whether 
these fragmentary and isolated forms of consciousness were any 


aid toward retaining the original learning is difficult to say. We. 


would hazard a guess that in many cases they were not an aid 
but actually a hindrance. At times pictures of previous chess 
formations would come to mind, and most of the subjects felt 
(rightly or wrongly) that these were a hindrance to them. » 

In the work interval the subjects seldom ever reported any 
return to consciousness of the original learning. The after-image 
or memory after-image was usually cut short in the work inter- 
vals. If the work became automatic, then the subject tended to 
think of the learning or wander off into more interesting fields. 
On the whole our subjects reported that the work kept them busy. 

We may here anticipate the introspective results for the non- 
sense syllable experiments following by saying that the rest inter- 
vals were much freer from any consciousness of the original 
learning than was the case with the reconstruction test. The 
sense words were more inclined to return to consciousness than 
either the reconstruction test material or the nonsense syllables. 


‘a> ae ae 


Pn OPE LM EN ATS OE OL LON 
SERIES OF TWELVE SENSE WORDS AS ORIGINAL LEARNING 


Will the same results found in the case of the reconstruction 
test likewise be found in the case of sense words? The following 
experimental section attempts to answer this question. In all 
the experiments reported in this section it is to be understood 
that the original learning consisted in a series of twelve sense 
words. The words were all one syllable, common words of 
three, four, and five letters (in a few cases six letters). The 
great majority of words were nouns, some verbs, and relatively 
few adjectives and adverbs. As far as possible the words in 
any one series were so chosen as to have little obvious relation 
between them. In all series the words were arranged in succes- 
sion, according to number of constituent letters, as follows: 4, 4, 
4,5, 3, 4, 5, 5, 3, 4,5, 4. As can be seen, the four-letter words 
predominated.. The same instructions were given the subjects 
concerning the work and rest intervals as stated in the last section. 


Experiment Series A. Comparison of Work versus Rest 
Intervals 


For various reasons, as will be mentioned later, this series of 
experiments falls into three groups, (1), (2), (3). 


Group (1) 


Two trained subjects did these experiments. The sense words 
were printed in large black typewritten type on 3” x5” cards. 
They were exposed serially and at the rate of one per 1.5 second 
by moving a long covering cardboard, containing a small lateral 
window cut into it, down the card. A silent swinging pendulum 
beat the time. 

The words were exposed just once, as we desired to secure 
but a faint impression. The words having been exposed, there 


36 ERNEST BURTON SKAGGS 


followed a work or a rest interval, as the case might be. The 
work consisted in adding ten one place numbers as fast and 
accurately as possible. One- and two-minute intervals were used. 
On any given experiment day six experiments were done, that is, 
three involving work and three involving rest intervals. Two 


minutes’ time elapsed between each experiment. Each day the 


order of the experiments was reversed, to-day being R, W, R, W, 
R, W, next time W, R, W, R, W, R. Each subject knew what 
kind of interval was coming next. The two subjects alternated 
in giving each other the tests, each subject doing his or her 
experiments every other day (9 A.M.). 

The following table gives the averages based upon twenty 
experiments for each work and rest interval, employing both 
one- and two-minute periods. Large R at the head of the 
column stands for the total number of words correctly recalled. 
Er. represents words recalled but which were incorrect. T 
signifies the time for recall. Figures in parentheses give mean 


variations. 
TABLE XXII 
One Minute Interval Two Minute Interval 
Work Rest Work Rest 


Roper Ls Re eee KRY? Bera: Re (hyo) 

LDS. 3.9004>.882 5.4 50.6) 828 3.0) 045.1970 7 Oe 
Caen) 24-0) eG pee) ON Ae ee OO ee 
BiB: 2.0 70.7 72.9. 2) Cine, AA eee 
(1. 1) (Oa) (18) (13) (08) (165) 43) 03) (12.9) (1.0) (0.5) (14.2) 
Inspection of the table shows clearly a retroaction in the case 
of LD.S. Subject E.B.S. indicates a slight tendency toward 
retroaction in the minute interval, whereas in.the two-minute 


interval no retroaction is found. 


Group (2) 

This group of experiments differs from the last in a number 
of respects. First, the order of presentation was irregular, and 
consequently S. did not know what interval was coming next. 
Second, only one interval was used, namely, a three-minute 
period. Third, S. worked only one minute, resting the last two 


~ 


FURTHER STUDIES IN RETROACTIVE INHIBITION 37 


minutes before recall. Fourth, two exposures were given instead 
of one. Fifth, the words were presented by a memory apparatus. 

The exposure apparatus used was a modification of the older 
Wirth machine made by Professor J. F. Shepard at the Univer- 
sity of Michigan. The series of sense words were written upon 
a strip of white paper in the same way as above mentioned. This 
strip was placed on the rotating drum of the machine and each 
word exposed serially at the exposure window. As there were 
fourteen stops during a complete drum rotation, and as we 
employed only twelve words, there was therefore an exposure of 
two blank spaces between the two exposures. 

The words were exposed serially at the rate of 1.5 second 
each, two exposures being given. The total exposure time was 
thus three seconds for each word. Each word was spoken aloud 
by S., who was instructed to take a discouraging attitude toward 
forming connections between the words. Other conditions were 
as in Group (1). 

Four trained subjects did these experiments. Table XXIII 
gives the means and mean variations (latter in parentheses). 
The averages are based upon nine experiments for each work 
and rest interval for all subjects excepting R.M.B., who has 


ten records. 
TRABLE XxX 





Work Rest Hour of 
Subject R Time Er. R Time Er. Experiment 
Shps. 7.0 77.4 0.3 yas Pane 0.78 11 a.m. 
(1.7) (30.4) (0.4) (1253) 01637 ee C0052) 
RS) 4.89 66.2 0.8 5.89 71.6 0.30 2:30 P.M. 
fey Cis.3)- (0,0) Cinco Los he COO.) 
R.M.B. Sed 82.5 0.2 4.89 ond 0.66 11 a.m. 
Creve (20) C0. 3) C196) eee 22015. C06) 
M.Bif. 5/8 48.6 0.8 6.10 50.3 0.78 1:30 p.m. 
Peso Cio, LO. 7) C1523) 016.2) (0:.69) 
Total PARSE Pa EN | ul ZAP 13 200"2 25, 
Mean 5.69 68.7 0.5 6.02 65.0 0.63 


The above table indicates, in the case of three subjects, some 
retroaction. However, the difference between rest and work 
intervals was small, while in the case of R.M.B. the rest interval 
was more unfavorable to retention and recall. While we may 
say that some retroaction is indicated here, the results are not 


38 ERNEST BURTON SKAGGS 


striking. The suggestion arose early that perhaps our work 
interval was too short. In consequence of the poor results 
obtained above, these experiments were discontinued and a third 
group begun. 

Group (3) 


The following experiments are exactly similar to the above in 


all respects except that the work was extended over two minutes 
instead of one. Thus we have two experiments : 

(a) The Work Series: Learn, work 2 min., rest 1 min., recall. 

(b) The Rest Series: Learn, rest entire 3 min., recall. 

The following table gives the means and mean variations for 
three trained subjects. All averages are based upon twelve 
experiments each for the work and rest conditions excepting in 
the case of F.C.D., who has fifteen records. 


TABLE XXIV 
Ly Work Rest Hour of 

Subject R Time ieler, R Time Er. Experiment 
F.C.D. Seek peu sD 0.33 6.07 56.5 0.2 8:20 A.M. - 

(1.51) (11.9). (0.53) (1.41) (12.8) (0.34) 
RS, 4.66 79.1 0.08 5.16 81.1 0.33 2:30 P.M. 

(1.56) (12.9) (0.15) (1.39) (8.81) (0.44) . 
M.BI. 4.92 63.1 0.5 6.17 63.8 1.0 1:30 P.M. 

(1.11) (10.3) (0.6) (1.19) (11.9) (0.8) 


In all cases in the table above we find that R for the rest 
condition is greater than R for the work condition. The rough 
time measurements signify nothing. Likewise a study of the 
errors made shows nothing definite. 

The experiments were also made upon five untrained subjects, 
students just finishing their first semester in the elementary labo- 
ratory course. They were given twelve experiments, six for each 
condition. Their averages are given in the following table. No 
mean variations are given. 





TABLE XXV 

Work Rest Hour of 
Subject R Time Er. R Time Er. Experiment 
R.M. 3.67 78.2 0.67 Seas 86.7 0.50 9 A.M. * 
H.G es, 84.7 0.17 7.00 67.0 0.30 4 P.M. 
idole: 5.58 92.8 0.25 5.58 80.2 0.40 11 A.M. 
G.J 5.00 69.9 0.67 7.00 69.0 0.67 1:30 P.M. 
E.D 3.20 43.4 0.00 2.80 49.0 0.20 4 P.M. 

Total. (22.78% 236920 1.76 25380 (B5109 2207 


Mean 4.56 FS ie Mirela NS 5.14 70.4 0.42 


i 


FURTHER STUDIES IN RETROACTIVE INHIBITION 39 


Two subjects do better after the work, two better after the 
rest, while one does the same in each, as regards R. The aver- 
ages for the group indicate a retroactive inhibition. While these 
results are not convincing, they indicate, if we take the group 
average, some detrimental influence. 


Experiment Series B. Effect of Practice 


In the table below we have summarized the averages for the 
first and last halves of three subjects’ completed records. The 
results are taken from a study of the individual records whose 
means are given in Table XXIV, preceding. 


TABLE XXVI 

Position Work Rest Retroaction 

Subject in Series R R (Rest-Work) 
M.BIE£. First Half 4.83 474 0.37 
Last Half 5.00 if Pe 2.20 
F.C.D. First Half 4.86 526 0.74 
Last Half 5.60 6.70 1.10 
RS: First Half 5.50 4.83 —00.67 
Last Half 3.83 5.50 1.67 


If we measure the amount of retroaction by the formula, 
R rest minus R work gives the amount of retroaction (where R 
stands for the amount recalled), then we find, in the case of the 
above named subjects, that as they become more practiced in the 
tests retroaction increases. This is true in every case. As our 
practice period is at most rather short, we can only say that within 
the limits of practice involved in our present experiments the 
retroaction became more marked as the practice increased. This 
is possibly due to the fact that our subjects constantly improved 
in ability to take an indifferent and passive attitude in the rest 
period. 


Experiment Series C. Position of Experiment in a Day’s 
Experiment Series 


If we take the rest and work intervals which occur in the 
first part of the day’s experimental series and compare the retro- 
action thus found with the retroaction found between work and 
rest intervals occurring in the last part of the day’s series, what 


40 ERNEST BURTON SKAGGS 


do we find? It will be remembered that a day’s experiment 
series consisted of six individual experiments. We have gone 
through the results for three subjects, whose means are given in 
Table XX VII, thus making the comparisons above stated. The 
following table gives the results: 


TABLE XXVII 


Position Retroaction 

Subject in Series R Work R Rest (Rrest-R work) 
BCs: First Half 5.78 O17 0.49 

Last Half 4.67 5.94 1227, 
R.S. First Half 5.00 5.60 0.60 

Last Half 4.20 4.86 0.66 
M.BIf. First Half 4.70 7.00 2.30 

Last Half Sea Ve anole 0.15 


The data are not uniform in indication. In the case of F.C.D. 
there is more retroaction for those experiments occurring near 
the end of the day’s series. The difference is marked and cor- 
responds to his introspections where he believes that he gets worse 
as the experiments progress in a given sitting. The record for 
R.S. shows nothing. On the other hand, M.BIf.’s record shows 
that there is more retroaction for those experiments occurring at 
the beginning of the day’s series. About all we can say is that 
we have found individual variation in this regard. 


Experiment Series D. Effect of Temporal Interpolation 


The method of presentation and material were as stated in 
Experiment Series A, Group (1), with certain changes. A short 
exposure or learning was again used, the series of words being 
presented two times. The work consisted in solving simple 
equation algebra problems. The total length of time between 
learning and the attempted recall was kept constant in all cases, 
namely, five minutes. The variable condition is the temporal 
position of the work. Four different conditions were used, as 
follows: 


(1) \-R3-W2e.. Tage t. Sa ee eee a ee Recall 
(2), L-R2-W2-RI1 wih o, | iva ceeieas doe cae eeCeE 
(3.)“L-=RISW2-R2Z 0a i es ae, Recall 
LAYS Toa W cI Bud one ioithuss ins tad hs aie tine a ee ea mene Recall 


All four experiments were done at one sitting, four minutes 
elapsing between the end of one experiment and the beginning 


FURTHER STUDIES IN RETROACTIVE INHIBITION 41 


of the next. The experiments were rotated from day to day. 
Excepting in the case of the last experiment of the day, the 
subject did not know, or very seldom, what kind of experiment 
was next. Unfortunately, only two subjects did this work, 
namely, I.D.S. and E.B.S., but for these two subjects the 
experiments were continued until their significance was clear. 

If the perseveration view is correct, and our work really 
involves a good type of concentrated activity, then we should 
theoretically expect to find least recall when the work followed 
immediately after the learning; then more recall for Method (3), 
more yet for Method (2), and most words recalled for Method 
(1), where we rest for three minutes after learning. 

The following table gives the results. The averages are based 
upon twelve experiments for each of the four different conditions. 
Experiments were done at 9 a.m. The figures in parentheses 
give the mean variations. 


TABLE XXVIII 
R3 W2 R2 W2 Ri R1 W2 R2 W2 R3 


R Er. AX R Er. Ak R Er. Aly R Er. T 
EBS eae PO. Selo Sco Su)e Us comer ous D 3:33 0.08 272.6 PSO Oe Sore 
(0.65) (20.0) (1.38) (13.0); (1.67) (13.6) (1.0) (14.8) 
LDS: 3,06 el, 80903 4.08 1.00 86.1 4.08 1.30 88.3 4.8 0.83 74.7 
(1.47) (21.8) (1.10) (17,4) C175) (28.3) (1.8) (18.7) 


Examination of these results shows diametrically opposed 
results. The record of E.B.S. is in accord with what we might 
theoretically expect from the standpoint of a perseveration view. 
The results of I.D.S. would indicate that she does best when the 
work is introduced immediately. However, the differences 
between the various methods are all very small and the safest 
thing to say is that this subject does not experience any greater 
retroaction when the work follows immediately. 


PART IV. EXPERIMENTAL SECTION 
NONSENSE SYLLABLES AS ORIGINAL LEARNING MATERIAL 


The following experiments attempt to give some light upon 
the same problems raised in the preceding experimental sections. 
However, in this section we have used nonsense syllables for the 
original learning. Nonsense syllables were used in one or the 
other of two forms, either as series of seven single syllables or 
as a series of seven paired syllables. Syllables having obvious 
meanings were thrown out. In any series we attempted to secure 
a balanced series of syllables with regard to difficulty of pronunci- 
ation. No two syllables in a given series began or ended with 
the same letter and no two syllables had two similar letters in 
order, as JEC, LEC. 


Experiment Series A. Using Single Syllable Series. 
Comparison of Rest versus Work Intervals 


The Shepard exposure apparatus, previously mentioned, was 
used. Seven nonsense syllables were typewritten in black large 
sized type upon a strip of white paper which was placed upon the 
drum of the exposure machine. As there were fourteen stops 
in a complete drum rotation, and inasmuch as we used only seven 
syllables, they were so arranged that every other stop of the 
drum gave a blank exposure. Each syllable was thus exposed 
for one second, then followed by a blank exposure; then the next 
syllable was exposed for one second, and so on. The tempo of 
the presentation was controlled by a silent swinging pendulum. 
The subject pronounced each syllable aloud once as it was 
presented. The syllables were exposed three times. 

After the exposure the experiment might take either of two 
forms, as follows: (1) a rest series of three minutes’ duration 
or (2) a work series, consisting of two minutes of concentrated 
work on mathematical or reasoning problems, such as the Thurs- 


FURTHER STUDIES IN RETROACTIVE INHIBITION 43 


tone series A and B; then subject rested one minute. The 
minute of rest, following the work, was used to give the subject 
a chance to rest and also to get away from the “ work attitude.” 
The subject then tried to recall all syllables possible. 

At one sitting six experiments were performed, three involving 
work and three involving rest intervals. Between two and three 
minutes elapsed between each experiment. Subjects I1.D.S. and 
E.B.S. alternated every other night as subjects in these experi- 
ments. The other subjects performed twice a week. 

The following tables give the averages for five trained subjects 
and fourteen untrained subjects. R stands for the number of 
correct reproductions; Er. for the errors; and T for the time of 
reproduction (taken with a stop watch). Half credit was given 
if two letters, in their proper sequence, were reproduced, as HIG 
for LIG. The time represents the interval between the signal 
for recall and the final statement of the subject that no more 
syllables would come (S. was asked not to “rack his brain”’ for 
the syllables). Again introspections have been carefully taken. 


TABLE XXIX 
SHOWING AVERAGES AND MEAN VARIATIONS FOR FIVE TRAINED SUBJECTS. 


Series A, SINGLE SERIES Non-SENSE SELLABLES. REST 
vs. Work INTERVALS 


Work Interval Rest Interval 
Subject R ai: Er. R Tr Er. 
Biss aol 24 0.54 4.23 82.2 0.54 
(1.15) (16.1) (0.48) (0:66) © C1837)" 0s} 
E.B.S. Zrl3 64.1 0.27 2:37 90.9 0.43 
(0.88) (16.2) (0.39) (0.96) (22.8) (0.52) 
F.C: 3.67 63.1 0.60 4.70 76.8 0.43 
AOrrao wt G18}9)> 9/(0..52) (i260 )s (2234 ees) 
M.BIf. 2.92 45.8 0.83 3.88 Sb 5 0.41 
Clyi7) 9a y7 (0.72) (0.75) (17.8) (0.49) 
Sw. 3.75 61.0 0.67 4.30 68.0 0.42 
(0°79 )o 0 Cla. aya OC 0,61) CE .00) = 613, OR const 


Notze.—R stands for number of syllables recalled; T, for time in seconds; Er., for 
errors. Figures in parentheses stand for mean variation. The times of day when each 
subject did the experiments and the number of records upon which the average is based are 
as follows: -D.S., 7 P.M., 14 records; E.B.S., 7 v.m., 15. records; F.C.D., 8 am,, 15 
records; M.BIlf., 1:30 p.m., 12 records; and Sw., 2:30 p.m., 12 records. 


44 ERNEST BURTON SKAGGS 








TABLE XXX 
Work Rest 

Sex R. Er ay R. ley “Ls 
Female iit eas 4.08 0.08 66.7 4.60 0.42 Gh 4 
Female’ scinsaiacatisietsste 2.92 1.08 122.0 Shay 1,83.) 13034 
Femaleticinica nanan 3.67 10041001326 BID 0.33 91.8 
Females esc eiai ees 3242 0.25 68.7 3.92 0.42 80.2 
Hemalece teen piaiine 3.42 0.25 56.3 3.43 1225 SleSe 
Bemalets ae cache ations 1275 202m 10652 3.92 19925 22208:.0 
M ale a oo a URN peice nan 2.75 0825 59.0 Zo 0.50 69.8 
Male Wht Aunt tee ve Gren 5.33 0.00 54.2 nes 0.30 86.0 
Malem rae raiies setae g 2107 0.00 46.0 HM oe NUR, 41.2 
Male unc maneneeen els 4.82 0.70 67.0 5e50) 0.30 69.0 
Maile se, nue ned oo Z10 0.75 Ties 3207: 0:60! ant 7/988 
Male ett ena s snare ea 2.83 0.33 57.2 3.25 0.25 520 
Male Raat ieee 3.75 1.10 0747, 4.50 0.50: sl07e3 
Maleate he tray ug 4.00 0.50 TZ 5.60 0.10 62.3 

Lotaliis seine mena eo 7.21 1048.8 57.48 8.89 1083.6 

IY Dee are heer a hele i Oe 3.39 0.52 74.9 4.10 0.64 77.4 

MEV Re io Arne OEE ts 0.71 0.79 


Table gives averages for 14 untrained subjects (elementary psychology students). 
Non-sense syllables, Series A. Experiments done at various times of day from 10 aM. 
nntil 5 p.m. Each average based upon six experiments, total experiments being 12. 


A study of Table XXIX (trained subjects) shows in every 
case that more syllables are recalled after the REST interval. 
While the difference between the two methods is indeed slight, 
yet it is consistent and argues for retroaction. The error columns 
show nothing significant. As regards time of recall, every sub- 
ject takes longer after the rest interval. The only plausible 
explanation we can offer for this is that after the work the syl- 
lables are gone so completely that, having reproduced a given 
number, the subject realizes the hopelessness of further attempt. 
Again, differences in attitude on the part of the subjects may 
possibly explain the situation. 

Table XXX gives the averages for fourteen untrained subjects, 
based upon six experiments for each of the two kinds of intervals. 
The students were in the writer’s elementary laboratory section, 
just beginning their laboratory work in psychology, and wholly 
ignorant of the purpose of the experiment. 

The averages for these untrained subjects indicate quite clearly 
retroactive inhibition. Taking the individual cases, we find that 
twelve out of fourteen show such retroaction. In one case the 
method used does not seem to matter, while in one other case 
the subject does better after the work interval. 


FURTHER STUDIES IN RETROACTIVE INHIBITION 45 


On the whole, the above experiments indicate clearly, we 
believe, a retroactive inhibition, a detrimental influence exerted by 
vigorous attentive work upon the original learning. 


Experiment Series B. Using Method of Paired Associates 


Testing (1) Rest versus Work Intervals. 
(2) Similarity of Work and Learning. 


In the following reported experimental section we have tried 
to get further data on (1) the comparison of rest and work inter- 
vals, and (2) by using relatively similar and dissimilar material 
in the work we have tried to find which type of work brings 
about the greater inhibition. In these experiments we have used 
two criteria for inhibition, namely, reaction times and the amount 
reproduced. 

Apparatus and procedure: The exposure apparatus previously 
mentioned was used, with a reaction time addition. An Hipp, 
spring driven, chronoscope was used for measuring the reaction 
times. It was used on a simple make-break circuit, the “ make ”’ 
occurring as the test syllable was shown in the exposure window 
and the “ break’ occurring as the subject released the teeth key. 
The chronoscope was kept tested by means of a gravity chrono- 
scope in which a steel ball, falling through one meter distance, 
operated the Hipp on a make-break arrangement. Our chrono- 
scope has been fairly constant for our purposes, having a constant 
error of 28.3 sigma, + 4.6 sigma. 

Seven pairs of syllables were exposed to the subject fifteen 
times by means of the rotating drum and control lever. A pause 
of two seconds occurred after the eighth exposure. Each pair of 
syllables was exposed for one and a half seconds. A blank space 
was shown at the window between each syllable exposure. The 
subject pronounced with equal emphasis each pair of syllables as 
it appeared. Having given the fifteen exposures, any one of the 
following three procedures might be followed: 

I. A rest period of five minutes. Test. 
II. A work interval using relatively dissimilar learning mate- 
rial. Here the work consisted either in working simple 


46 ERNEST BURTON SKAGGS 


arithmetic or algebra problems or else in reasoning out the 
Thurstone reasoning problems. The work lasted for 
three minutes, then a rest of two minutes ensued. Test. 


III. A work interval using relatively similar material.  S. 
studied another set of seven syllables for one minute; 


worked for one and one-half minutes on the same material 


as given in II above; recalled syllables from the work 
series for one-half minute; rested two minutes. Test. 


As will be seen, the total time between learning and testing is 
in all cases five minutes. In the test for recall the syllables con- 
stituting the left side of the pair (from the subject’s side) were 
presented and in the following sequence: 5, 7, 1, 3, 6, 2, 4. 
(These numbers refer to the position of the syllables in the 
original learning.) The subject reacted by speaking aloud the 
associate syllable as soon as the syllable came to mind, or in case 
nothing came, the subject signified by saying “nothing.” In 
either case the speaking broke the electrical contact and +e 
the chronoscope. 

The following tables give the results in terms of reaction times 
and number of associates reproduced, along with errors. We 
have treated the reaction times in three ways: (1) We have 
picked out from our records the wholly correct associates and 
thus compared the three methods; (2) we have combined the 
wholly right and half right associates; (3) all association times 
have been lumped together for each method used and thus com- 
pared. iis thus include right, half right, errors, and reaction 
times giving “ nothing.” 

If there is a positive retroaction it ought to be manifest in a 
comparison of Method I with either of the other two methods, 
II and III. We should expect the shortest reaction times for 
Method I, involving the rest interval. These results are found 
for only two subjects, F.C.D. and I.D.S., in the case of the right 
associates. For the other three subjects the data are conflicting— 
at least not clear. If we consider the times for correct and half 
correct associates, we find no evidence for retroaction in the case 
of any subject. Taking the association times for all reactions 


a; 


FURTHER STUDIES IN RETROACTIVE INHIBITION 47 


TABLE XXXI 
REACTION T1MEs, FivE TRAINED SUBJECTS 
Times for Correct Times for Correct Times for All 
Associates and Half Correct Reactions 
Subject I II III I II Wy I II Ill 


F.C.D. 3594 4664 4300 4782 4935 4320 6931 7398 5949 
(3126) (3445) (2839) (4104) (3423) (2736) (5929) (5550) (3919) 

N,31 N,35 N,37, N39 N34 N56 N62 N,54 

LD.S. 2443 2358 3840 2619 2419 3283 3686 3829 4605 
(1362) (1244) (1757) (1555) (1265) (1766) (2312) (2155) (2078) 

N,43. N41. N39 N48 N,43. N42 N,79 N82 N82 

E.B.S. 3333. 2790 «-.2734:«=S3688.-«2799:« 2907» 4801 4696 4489 
(1856) (1272) (1271) (1962) (1195) (....) (2280) (1918) (1945) 

N,29 N,25 N32. N33 N26 N38 N,83 N80 N,79 

M.BIf. 3074 2866 3490 3314 2785 3460 4378 4062 5029 
(1225) (1220) (2100) (1474) (1163) (1970) (2342) (2615) (2510) 

‘N,23. N28 N,19 N,31 N30 N,25 N56 N54 N,55 

Swk. 3888 4689 3669 3972 4526 3800 6530 7756 7188 
(2817) (3117) (1791) (2697) (2993) (2283) (4778) (5686) (4847) 

2 N,25 N,30 N,24 N30 N33. N,26 N63 N,55 N,52 

roup 


Deans) 93260)" 3474013547.) 3675.» 3493) (28572) 5283) 554865452 


In the table above the four place figures give the reaction times in sigma and are 
averages. The figures-in parentheses are mean variations. N stands for the number of 
cases. Column headed I refers to Rest Interval; II, the Work Interval using Dissimilar 
work material; III, the Work Interval involving Similar work material. 





TABLE XXXII 
Amount, RECALLED AND Errors, FivE TRAINED SUBJECTS 


I. Rest II. Work, Dissimilar III. Work, Similar 

Subject R Er. R Er. R Er. 
E.B.S. 2.83 0.70 3.08 0.46 2525 0.67 
(1.08) (0.74) (1.24) (0.38) (0.75) (0.38) 

TDS: 4.20 1.30 BisfAl 0.79 e/5 Tal 
(0.99) (0.73) (1.47) (0.45) (1.00) (0.64) 

Swk. aal5 1.65 4.55 1.39 3.83 1.00 
(0.80) (0.85) (1.01) (0.77) (1.41) (1.00) 

M.BIf. 3.50 1.89 3.88 E25 2.88 2/5 
(0.63) (0.57) (0.78) (0.94) (0.47) (0.75) 

GD: 4.00 1.60 4.22 1.00 4.25 1R62 
(1.00) (0.75) (0.96) (0.66) (0.94) (1.03) 

Group Mean 3.54 1.43 3.89 0.98 3.39 1.44 


Figures given in table are averages. Figures in parentheses give the mean variations. 


under each method, we again find our results conflicting. Subjects 
Swk. and I.D.S. alone give data suggesting retroaction. 

Table XXXII gives the amount of recall and errors under the 
headings R and Er., respectively. Comparing the results again 
as regards the rest as over against the two work intervals, we find 
that only one subject, I.D.S., indicates retroaction. Likewise the 


48 ERNEST BURTON SKAGGS 


group average signifies nothing. A study of the errors made 
also seems fruitless. 

Our work (repeating in many ways the work of DeCamp) with 
the paired associates method has been largely barren of results. 
Strangely enough, we secure evidence of retroaction for single 


series of syllables, but our results are conflicting and often the 


very reverse of expectation when we used the paired associates 
material. Our only explanation is that fifteen exposures in this 
case fixes the associations too securely to permit retroaction. 
However, this hypothesis hardly seems justifiable as we review 
the struggles of the subject to recall the associate. A series of 
experiments must be carried on in which the number of exposures 
is greatly reduced in order to test this point. 

The second problem investigated in this section has to do with 
the question of the degree of similarity of the work and learning 
material. A review of the two preceding tables gives the results 
for five trained subjects. The reaction times for Methods I and 
II (Table XX XI) show only two cases, when right associates are 
taken, where the similar work material exerts a greater retroaction 
than the dissimilar. For the other four subjects the reverse is 
true. The other studies of the times in the table are likewise 
conflicting. If the more similar work material exerts greater 
retroaction than the dissimilar, then we might expect a longer 
reaction time in the former case. Our results do not indicate 
that such is the case under the conditions of our experiment. If 
we turn to the errors and amount recalled (Table XXXII) we 
find some evidence that the more similar work exerts greater 
retroaction than the less similar. In three cases R is less for 
the similar work than for the dissimilar, and in the two cases 
where the reverse is found the difference is very small. Taking 
the group averages, there is a slight advantage in the case of the 
dissimilar work. If we overlook the fact that our reaction times 
failed to reveal anything, our evidence indicates that the more 
similar the work and learning, the greater is the retroactive effect. 





FURTHER STUDIES IN RETROACTIVE INHIBITION 49 


Experiment Series C. Single Syllables 
Similar versus Dissimilar Work 


In the following section we have used eight untrained subjects 
and single series of nonsense syllables. The series of seven 
syllables was exposed on the rotating drum at the rate of one per 
1.2 seconds. Three exposures were given, the subject saying 
aloud each syllable as it came to view. After the exposure S. 
either worked for three minutes on Thurstone reasoning prob- 
lems or else worked for two and one-half minutes studying 
fourteen new syllables, taking the last half minute to recall these 
syllables. Six experiments were done at one sitting. Each sub- 
ject did his experiments at the same time of day, although 
different subjects did their work at different times. 

There were four men and four women, all elementary psy- 
chology students having had some laboratory work but no previ- 
ous work with nonsense syllables. They merely knew the general 
nature of the experiment, namely, that it had to do with inhibition. 
In the recall the first syllable was always given to the subject. 
A perfect recall would thus be six syllables. The time taken in 
recall was measured by a stop watch. The following table, 
XXXIII, gives the individual and group averages : 


TABLE XXXIII 








Similar Dissimilar 
R Br T R Ds 5 ah 
0.83 1.70 104.8 1.88 1.50 15120 
175 0.25 45.2 2.92 0.25 48.3 
0.90 0.50 88.2 2.60 0.50 116.4 
1.92 0.75 92.5 2.00 0.67 92.3 
1.00 0.83 46.5 tego (aos 75.0 
126 7eeee Vl 500 insteds Ze25 1.08 116.7 
Beas 0.50 128.7 3.83 0.50 141.3 
2.08 5.83 103.0 Dros st gly 140.7 
Total 12.48 11.36 622.4 19.14 6.00 881.7 
Mean 1.56 1.42 77.8 2.36 EVE: LOR? 
M.V. 0.48 0.54 


Without exception, every subject recalled more syllables when 
the work was dissimilar. Likewise the errors made are greater 
in the case of the similar work. The similar work apparently 
involves a greater retroaction. 


50 ERNEST BURTON SKAGGS 


Experiment Series D. Effect of Varying Temporal Position of 
Interpolated Work, Single Syllables 


In the following report series of seven nonsense syllables were 
used as the original learning material. The method of exposing 
and learning was similar to that in Experiment Series C. The 
interpolated work consisted in working algebra and arithmetic 
problems, and, as such, was a constant condition. The con- 
dition which we have tried to vary is the length of time elapsing 
between original learning and work interpolation. The total time 
was the same for each experiment, namely, six minutes. Three 
variant intervals or combinations were used, as follows (figures 
indicating minutes) : 

I, L—W3—R3—Test. 
Il. L—R1—W3—R2—Test. 
Ill, L—R3—W3—Test. 


On any experiment day six experiments were done; that is, 
each of the above three was done twice. An interval of from 
two to three minutes intervened between each experiment. In the 
test E. gave S. in every case the first syllable. Thus there 
remained six syllables to be reproduced. Half credit was given 
for those syllables in which two consecutive letters were correct. 

In the following table, XXXIV, are given the results from 
five trained subjects. The column headed R gives the average 
amount reproduced (six being a perfect score); Er. stands for 
the average error; and T signifies the time taken in recall. 
Unfortunately, the experiments had to be done at different times 
of day. E.B.S. and I.D.S. did their experiments at 7 pP.M.; 
F.C.D., at 8 a.m.; Swk., at 2:30 p.m.; and BIf., at 10 a.m. 

Taking first the group average, it will be noted that, while the 
difference is not great, there is a better recall when a rest interval 
of three minutes intervenes than when the work is introduced 
immediately. The intermediate combination II, however, gives’ 
the best results. The averages for this intermediate method are 
based upon relatively few records (unfortunately) in the case of 
three subjects. 

Studying the data by subjects, we note that I.D.S: and E.B.S. 


FURTHER STUDIES IN RETROACTIVE INHIBITION 51 


give rather clear results, a decreasing value of R as we read 
across the table from left to right. F.C.D. and Swk., while 
doing better (apparently) by the Method II, yet indicate in their 
averages that there is more retroaction when the work is intro- 
duced immediately than when a rest of three minutes intervenes. 
Blf. alone fails to indicate a greater retroaction when the work 
is introduced immediately. On the whole the data of Table 
XXXIV indicate that work introduced immediately after learning 
gives the greatest retroaction. 

As a check series some further experiments were done with 
thirteen untrained subjects. These experiments were similar to 
the above excepting that the total time was seven minutes rather 


TABLE XXXIV 


L-R3-W3 L-R1-W3-R2 L-W3-R3 
Subject R Er. a8 R Er. Ai R lie fh 
E.B.S. 2.04 0.80 97.3 145 0.45 82.5 1.30 0.62 70.4 
(0.97) (0.63) (16.8) (1.04) (0.58) (20.5) (0.10) (0.50) (25.4) 
Dae ey rae 2 NTE ONE oe tg N IZ GN IZ NZ 


LDS. 3.497 0.33." 63.0 3.10 0.40 65.4 2.63 0.88 64.0 
(1.04) (0.44) (20.0) (1.22) (0.40) (17.7) (1.15) (0.86) (20.7) 

Pyec te, NZ ON IO NAG CN LOPS N 12 NZ Ne 

FED; axa08: 1.600 -72.0 5.20 0.20 59.0 295 0.55 71.0 
(1.24) (0.46) (25.0) (0.32) (0.32) (22.0) (1.17) (0.54) (19.0) 

N,10 N10 N,9 Nios SSRN N,10 N,10 N,10 

Swk. Soe. Won 77.1 4.67 0.00 64.5 2.85 1.05 100.3 
(0.67) (0.36) (22.9) (0.89) (0.00) (19.5) (1.05) (0.47) (22.9) 
N,10 N,10 N,10 N6 N6 N,6 N,10 N,10 N,10 

Bif. Boe as. | 94.6 430 086 41.7 4.20 040 51.5 
(1.04) (0.68) (10.6) (0.33) (0.49) (6.6) (1.04) (0.32) (6.8) 

N,10 N,10 N,10 Res Beg ds iar N,10 N,10 N,10 

Group Aver. 3.22 0.58 73.8 3.75 0.38 62.6 2.792 0 707 A 


Figures in parentheses give M.V. WN signifies number of experiments. 





than six. In all cases S. spent the last minute just before recall 
in glancing through a magazine. Only two combinations were 
used, the I and III above. 

Table XXXV gives the results. The averages are based upon 
only four experiments for each combination. The work con- 
sisted, on the first experiment day, in working out Thurstone 
reasoning problems and, on the second day, doing simple algebra 
and arithmetic problems. 

The above table indicates nothing definite. The group aver- 
ages indicate a slightly greater recall when a rest period inter- 


De ERNEST BURTON SKAGGS 
TABLE XXXV 

















R2 W3 M1 W3 R2 M1 

Sex R Er. ah R Er. Az 
Male iets Ue ears S355) 0.75 O1eZ Shs 0.75 58.2 
Males cee ee ia e218 0.50 70.2 Pas 1.00 68.5 
Malerget cere 1.6 0.88 Fis 0.8 2.00 81.0 
Male.... ath 235 1.50 78.2 $395, 1.12 108.0 
Female. . 2.9 1.38 98.2 3.6 12412 JaaG 
Male.... BS 0.50 40.9 2.5 0.50 40375 
Male trivetnicsc ays 0.62 41.5 Sioa! OF38 822 
Female.... 40) 0.88 104.7 3.0 0.38 9725 
Malet aineias 2.6 0.12 Sie/ he: 0225 Sono 
Malepeua. 2ro 0.25 48 .2 BASS 0.25 49.0 
Female bir)... Shel 1.10 74.8 2.0 0:50). 1012 
Pemalesiay 2) 4.2 0.88 45.0 Say 1.00 56.7 
Male taiynay. 223 0.75 47.0 3 1225 S162 

Total, eee kien cid ot OLA Pe Led e757 2 35.4) 1 0u50 Msooes 

Mitel Rik, aitedleaech cee wea, 28 OD tet OOO 67.3 PAVE NU EAW bY) iS. 

Mr Nee Pepa dt crete eects aa GO PMOL 18.6 0273000241 20.2 


venes before the work, as compared to the condition where the 
work comes immediately. Seven individuals show greater retro- 
action when the work comes immediately, while six give opposite 
results. 

Basing our statement on the work of the trained subjects, we 
may say that there is a positive indication that the temporal 
position of the work is important. 


Experiment Series E. Effect of Varying Temporal Position 
of Work, Paired Associates Method 


The problem investigated in this series is the same as that 
considered in the Series D preceding. However, we have here 
tried to test the matter of the importance of the temporal position 
by using the paired-associates method. The arrangement of the 
pairs, their presentation, and method of testing was the same as 
mentioned in Series B preceding. Two different methods were 
used and compared, as follows: 


I. L (15 exposures )—W3—R3—Catalogue 1—Test. 
II. L (15 exposures )—R3—-W3—Catalogue 1—Test. 


In each of the above methods the subject spent the last minute 
glancing at the pages of an apparatus catalogue. The records of 
five trained subjects appear in the following tables, XXXVI and 


FURTHER STUDIES IN RETROACTIVE INHIBITION 53 


XXXVII. Three experiments were done at each sitting, two of 
one method and one of the other. On the day following, this 
was reversed. The subjects did their experiments at the same 
times as mentioned in Series B. The presentation of the methods 
was irregular and S. did not know what to expect next. Table 
XXXVI gives the means, the mean variations (figures in paren- 
theses), and the number of experiments upon which the means 
are based. These means represent the average number of syl- 
lables (associates) reproduced correctly (column headed R), and 
the errors (column headed Er.). Table XXXVII gives the 
reaction times in sigma, the mean variations, and the number 
of cases. 
TABLE XXXVI 


: R3 W3 Cl W3 R3 Cl 

Subject R Er. R Er. 
LE 0 ED rly A? SG Ea 4.07 1d 4.36 1.07 
R123) (0.80) (0.77) (0.80) 

N,7 N,7 N,7 N,7 

MESO cas ine es cca ee ree. 3.61 1.94 255 2.67 
(1 ve ee (1.42) (0.99) 

$ ’ 9 > 

Ge RS A ee ee 5.00 1.00 4.11 1.00 
(1.22) (0.55) (1.12) (0.67) 

9 N,9 9 : 

EAL SSE RE 1 ls a abe 28 2.81 0.89 2251 0.96 
(0.98) (0.46) (1.30) (0.88) 

N,13 N,13 N,13 N,13 

TULD anes fF Circa y 6a Oso oie eae 4.40 1.50 4.80 1.00 
(1.30) (0.83) (0.73) (0.33) 

N,l1 N,11 N,12 N,12 

GroupeVlcanedy.). «2. cikvelne o/s 3.98 1.38 3.67 1237 


Studying Table XXXVI, we note that the group average indi- 
cates an advantage with regard to amount reproduced for the 
method in which a rest interval of three minutes intervenes 
between the original learning and work. The errors are the 
same. Three subjects give more associates when the work is 
delayed, whereas in two cases (I.D.S. and Swk.) there is a 
slight advantage for the method which involves the immediate 
introduction of the work. 

Turning now to the reaction times (Table XXXVII) and 
inspecting first the group average, we note, for the correct asso- 
ciates, that the mean reaction time is 125 sigma longer when the 


54 ERNEST BURTON SKAGGS 


work is introduced immediately. Considering columns three and 
four in the table, which give the times for both correct and half 
correct associates reproduced, we find the same thing, excepting 
that here the difference is greater, namely, 369 sigma. It will be 
noted that in the case of Swk. we have used a smaller set of means 
than that listed above his mean variations. We have taken out ~ 
three very extreme times from his records and this gave us the 
smaller averages. These extreme records were thrown out as 


TABLE XXXVII 
Reaction Times Reaction Times 


for Wholly for Correct and Half 
Correct Associates Correct Associates 
Subject R3 W3 Cl W3R3 Cl R3 W3 C1 W3R3 C1 

Sik Peete aahte tater eae 6026 3965 5564 5375 
(4921) (2557) (4268) (3516) 

N,24 N,27 N,30 N,34 

*3967 3472 3702 3418 

Hey hit Rep el Reg WERE a Rhee Le iy 2701 2465 2699 2903 
(1401) (1248) (1327) (1739) 

N,30 N,20 N,33 N,26 

| WN CEI Ds Batre syed Pie ai HAS A He 4149 4580 4111 5236 
(2898 ) (3081) (2768) (3709) 

N,43 N,3 N4 537, 

FYB AS 2 si enbhorie durante 2775 2368 2941 MPAIER. 
(1496) (1408) (1583) (1381) 

N,34 N,32 N,37 N,33 

6B eS aa) A 1 AL Si 2327 3660 2447 3854 
(1253) (2334) (1370) (2502) 

N,43 N,54 N,48 N,62 

Gr OUD iM Caney hace isos «suit 3184 3309 3180 3549 


* This row of means used in all calculations. 


the subject reported that he had the associate but held on to it 
overtime. Consequently we have used his smaller average, in 
which these three very extreme reaction times are omitted from 
consideration. 

Subject Swk. gives a reaction time longer for Method II, 
although this difference stands out greater than the difference 
between the two methods as regards amount reproduced. About 
the same can be said for E.B.S., his reaction times being shorter . 
when he works immediately after the learning. F.BIf. gives a 
shorter reaction time for Method I (immediate work) in case of 
correct associates. However, when we consider together the 
correct and half correct associates given the reverse is. true. We 


FURTHER STUDIES IN RETROACTIVE INHIBITION 55 


are inclined to stress columns III and IV in our table above for 
it is these half correct associates which represent the hesitations 
and blockings noted in the subject’s reactions. Considered from 
the standpoint of either correct or correct and half correct asso- 
ciates, the results from F.C.D. show a longer reaction time when 
the work follows immediately. While, as we saw above, I.D.S. 
reproduces as many associates for Method I as for Method II, 
a study of the reaction times gives a clear case for Method II. 
The reaction times are longer when the work is introduced 
immediately. 

We believe that a careful analysis of the above results justifies 
us in saying that the temporal position is important—that work 
introduced immediately causes more retroaction (as judged by 
‘a longer reaction time and a smaller number of recalled associates ) 
than the method wherein the work is not introduced until after 
three minutes. We have some individual (apparent) exceptions. 
Some other form of work activity, a longer period of work 
activity, less number of exposures in the original learning—these 
and other differing conditions might have yielded us, even for 
these apparent exceptions, results confirmatory of our above 
generalization. Certainly we must say that there seem to be 
individual differences indicated as regards susceptibility to retro- 
action in the above experiments. The work in Series D, using 
single syllables, likewise lends weight to our generalizations as 
stated above. 


PART V.. EXPERIMENTAL SECTION 
GENERAL SUMMARY OF THE INVESTIGATION 


There remains the task of bringing together the results of the 
various experimental series. 

I. The experiments involving the reconstruction test for origi- 
nal learning indicate very clearly that it is better to rest after the 
learning than to turn immediately to some other vigorous and 
taxing work. That is to say, learning after a rest interval can 
be recalled better than after a work interval. 

The same results have been found in the case of series of 
sense words as original learning. Likewise the use of single 
series of nonsense syllables showed the same results. However, 
when we used series of paired associates and tested by the 
method of right associates and reaction times, our results were 
conflicting. 

II. Our data indicate that the degree of similarity between the 
original learning and the interpolated work activity is important. 
Within limits, the more similar the original learning and the 
interpolated work the more detrimental will be the effect upon 
the efficiency of recall of the original material. The matter of 
“within limits ’’ must be stressed here. The data from the recon- 
struction test is quite definite in justifying the above statements. 
In the case of single series of nonsense syllables it was also found 
that the more similar the work and learning material the greater 
the detrimental influence on recall of the original learning. Again, 
the reaction times of the paired-associates (nonsense syllables) 
experiments failed to give clear results, although the amount 
reproduced indicates a greater retroaction when the work and 
learning are similar. 

Our work substantiates Robinson’s results in the matter of the 
importance of the degree of similarity of work and original 
learning. We must hasten to add certain limitations and 
additions to the general statements preceding : 


FURTHER STUDIES IN RETROACTIVE INHIBITION 57 


A. When work and original learning are identical in content 
and method there is only reinforcement or repetition, There 
is no inhibition. 

B. As the material is made (by degrees) more and more dis- 
similar the reinforcing factors gradually diminish in effec- 
tiveness and the interfering factors become more and more 
pronounced. 

C. As the material of learning and work is made more dis- 
similar a point is reached where there is a maximum of 
interference or detrimental influence wrought upon the 
original learning. 

D. Beyond this point the curve of interference or detrimental 
influence goes downward, and then we can say that the 
more dissimilar the materials the LESS the detrimental 
influence. 

E. However, the curve of detrimental influence never reaches 
zero because after the work and learning are as different 
as can possibly be made there is still a damaging influence 
exerted by the work. 


We have found it very difficult to make out a graded series of 
work activities differing in degree of similarity from the original 
learning. 

III. All the data which we have accumulated indicate that the 
temporal position of the interpolated work is important. Work 
introduced immediately following the original learning is more 
detrimental in its influence on that original learning than work 
introduced after a rest interval. Reconstruction test data, single 
series of nonsense syllables, and paired series of nonsense syl- 
lables indicate the above conclusion. The little work done with 
sense words alone is conflicting. 

These results confirm the results found by Muller and Pilzecker 
and are opposed to the findings of Robinson, who rejects the 
matter of temporal position of the interpolated work as unim- 
portant. 

IV. On the basis of the data from the reconstruction experi- 
ments there seems evidence that as the subject becomes more and 


58 ERNEST BURTON SKAGGS 


more fatigued in the course of the day’s series the work activity 
acts relatively more detrimentally upon the original learning. 

Tolman found that there is a more detrimental influence of 
work upon learning in the evening than in the morning. Our 
investigation of the relative effects of work activity in the morn- 
ing and evening, however, fail to confirm Tolman’s conclusions. 
When learning was as good in the evening as in the morning 
there was no evidence that the work interpolated was more 
detrimental. 

V. As regards the effects of practice, our data are not as 
positive as we would wish. As the subject becomes more and 
more practiced with the original learning material will there be 
less and less detrimental influence exerted by the work activity? 
Robinson has suggested this. In the case of the sense words 
our results actually indicate that as the subject becomes more 
practiced there is an increase in the detrimental action of the work 
material. The results from the reconstruction test are conflicting. 

Our data show that as the subjects become more practiced with 
the original learning material the learning itself is better, the 
subject learns more easily, and can retain longer. Certain effi- 
cient methods of learning become selected by the trial and error 
process as one becomes practiced with a given learning material. 

VI. Certain general statements may be made here concerning 
the rest and work periods. Two years of working on this inves- 
tigation have emphasized to us the following points: 

A. Trained subjects are a necessity. One cannot know about 
the nature of the “ rest’ interval unless the subject gives a 
detailed and careful report of what went on ‘“ within.” 
Only the subject can tell whether the work activity was 
“difficult or easy,” “interesting or boresome, attentive 
or inattentive,” etc. 

B. The number of “ rest” intervals which are near ideal from 
the standpoint of “‘ mental passivity’ and absence of all 
thought of the original learning is relatively few. Most 
rest intervals are characterized by either some “ return ”’ to 
consciousness of the original learning or else the subject 
becomes active mentally upon some line of thought. 


99 66 


FURTHER STUDIES IN RETROACTIVE INHIBITION 59 


C. As subjects become practiced they are better able to take 
an indifferent and passive attitude during the rest interval. 

D. In most cases where there was reported some consciousness 
of the original learning during the rest interval it was very 
vague and fragmentary, often taking the form of merely 
desiring to recall it with a feeling that it was near at hand. 

E. It is important that work which will combine interest and 
maximum effort be secured for the work activity. We have 
found reasoning problems of a logical and mathematical 
nature the most satisfactory work material. 


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